Drop asciidoc partintro formatting

Since to no longer use docbook, we can't use `partintro`.

See gh-12005

spring-boot-project/spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -2,15 +2,12 @@
 = Build Tool Plugins
 include::attributes.adoc[]
 
-[partintro]
---
 Spring Boot provides build tool plugins for Maven and Gradle. The plugins offer a variety
 of features, including the packaging of executable jars. This section provides more
 details on both plugins as well as some help should you need to extend an unsupported
 build system. If you are just getting started, you might want to read
 "`<<using-spring-boot.adoc#using-boot-build-systems>>`" from the
 "`<<using-spring-boot.adoc#using-boot>>`" section first.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/deployment.adoc

@@ -2,14 +2,11 @@
 = Deploying Spring Boot Applications
 include::attributes.adoc[]
 
-[partintro]
---
 Spring Boot's flexible packaging options provide a great deal of choice when it comes to
 deploying your application. You can deploy Spring Boot applications to a variety
 of cloud platforms, to container images (such as Docker), or to virtual/real machines.
 
 This section covers some of the more common deployment scenarios.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/documentation-overview.adoc

@@ -2,11 +2,8 @@
 = Spring Boot Documentation
 include::attributes.adoc[]
 
-[partintro]
---
 This section provides a brief overview of Spring Boot reference documentation. It serves
 as a map for the rest of the document.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/getting-started.adoc

@@ -2,14 +2,11 @@
 = Getting Started
 include::attributes.adoc[]
 
-[partintro]
---
 If you are getting started with Spring Boot, or "`Spring`" in general, start by reading
 this section. It answers the basic "`what?`", "`how?`" and "`why?`" questions. It
 includes an introduction to Spring Boot, along with installation instructions. We then
 walk you through building your first Spring Boot application, discussing some core
 principles as we go.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/howto.adoc

@@ -2,8 +2,6 @@
 = "`How-to`" Guides
 include::attributes.adoc[]
 
-[partintro]
---
 This section provides answers to some common '`how do I do that...`' questions
 that often arise when using Spring Boot. Its coverage is not exhaustive, but it
 does cover quite a lot.
@@ -15,7 +13,6 @@ the `spring-boot` tag).
 
 We are also more than happy to extend this section. If you want to add a '`how-to`',
 send us a {github-code}[pull request].
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -2,13 +2,10 @@
 = Spring Boot Actuator: Production-ready Features
 include::attributes.adoc[]
 
-[partintro]
---
 Spring Boot includes a number of additional features to help you monitor and manage your
 application when you push it to production. You can choose to manage and monitor your
 application by using HTTP endpoints or with JMX. Auditing, health, and metrics gathering
 can also be automatically applied to your application.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-cli.adoc

@@ -2,13 +2,10 @@
 = Spring Boot CLI
 include::attributes.adoc[]
 
-[partintro]
---
 The Spring Boot CLI is a command line tool that you can use if you want to quickly develop
 a Spring application. It lets you run Groovy scripts, which means that you have a familiar
 Java-like syntax without so much boilerplate code. You can also bootstrap a new project or
 write your own command for it.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2,14 +2,11 @@
 = Spring Boot Features
 include::attributes.adoc[]
 
-[partintro]
---
 This section dives into the details of Spring Boot. Here you can learn about the key
 features that you may want to use and customize. If you have not already done so, you
 might want to read the "<<getting-started.adoc#getting-started>>" and
 "<<using-spring-boot.adoc#using-boot>>" sections, so that you have a good grounding of the
 basics.
---
 
 
 

spring-boot-project/spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -2,8 +2,6 @@
 = Using Spring Boot
 include::attributes.adoc[]
 
-[partintro]
---
 This section goes into more detail about how you should use Spring Boot. It covers topics
 such as build systems, auto-configuration, and how to run your applications. We also
 cover some Spring Boot best practices. Although there is nothing particularly special
@@ -13,7 +11,6 @@ recommendations that, when followed, make your development process a little easi
 If you are starting out with Spring Boot, you should probably read the
 _<<getting-started.adoc#getting-started, Getting Started>>_ guide before diving into this
 section.
---