Add spring security saml dependency to docs

spring-boot-project/spring-boot-docs/pom.xml

@@ -947,6 +947,11 @@
 			<artifactId>spring-security-oauth2-resource-server</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-saml2-service-provider</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.security</groupId>
 			<artifactId>spring-security-test</artifactId>