[Test] Reorganize Maven repository configuration in build.gradle

Repo https://snapshots.elastic.co/maven/ is no longer needed in a
composite build. Previously it was only used to provide snapshot version
 of `elasticsearch-java` client which is no longer available in snapshot
  version. We keep the https://snapshots.elastic.co/maven/ repo to be
  used when for non-composite builds when any other dependencies
  snapshot versions can be fetched.

Author: jozala

plugins/examples/build.gradle

@@ -22,22 +22,16 @@ subprojects {
 
   repositories {
     // Only necessary when building plugins against SNAPSHOT versions of Elasticsearch
-    maven {
-      url = 'https://snapshots.elastic.co/maven/'
-      mavenContent {
-        if (gradle.includedBuilds) {
-          // When building in a composite, restrict this to only resolve the Java REST client
-          includeModule 'co.elastic.clients', 'elasticsearch-java'
-        }
-      }
-    }
     if (gradle.includedBuilds.isEmpty()) {
       maven {
         url = "https://artifacts-snapshot.elastic.co/elasticsearch/${elasticsearchVersion}/maven"
         mavenContent {
           includeModule 'org.elasticsearch', 'elasticsearch'
         }
       }
+      maven {
+        url = 'https://snapshots.elastic.co/maven/'
+      }
     }
 
     // Same for Lucene, add the snapshot repo based on the currently used Lucene version