Convert string to integer for ulimits.nofile

Before this commit:

> make overview metrics
services.rmq1.ulimits.nofile.hard must be a integer
make: *** [Makefile:68: overview] Error 15

Accoring to the docs
https://docs.docker.com/compose/compose-file/compose-file-v3/#ulimits
this must be an integer.

deps/rabbitmq_prometheus/docker/docker-compose-dist-metrics.yml

@@ -41,8 +41,8 @@ services:
     # we want to simulate hitting thresholds
     ulimits:
       nofile:
-        soft: "2000"
-        hard: "2000"
+        soft: 2000
+        hard: 2000
   rmq1-dist-metrics:
     << : *rabbitmq
     hostname: rmq1-dist-metrics

deps/rabbitmq_prometheus/docker/docker-compose-dist-tls.yml

@@ -41,8 +41,8 @@ services:
     # we want to simulate hitting thresholds
     ulimits:
       nofile:
-        soft: "2000"
-        hard: "2000"
+        soft: 2000
+        hard: 2000
   rmq1-dist-tls:
     << : *rabbitmq
     hostname: rmq1-dist-tls

deps/rabbitmq_prometheus/docker/docker-compose-overview.yml

@@ -38,8 +38,8 @@ services:
     # we want to simulate hitting thresholds
     ulimits:
       nofile:
-        soft: "2000"
-        hard: "2000"
+        soft: 2000
+        hard: 2000
   rmq1:
     << : *rabbitmq
     hostname: rmq1