Remove integration testing using OSS distribution (#69153)

plugins/examples/painless-whitelist/build.gradle

@@ -22,7 +22,7 @@ dependencies {
 }
 
 testClusters.all {
-  testDistribution = 'OSS'
+  testDistribution = 'DEFAULT'
 }
 
 tasks.named("test").configure { enabled = false }

qa/build.gradle

@@ -1,17 +1,9 @@
-import org.elasticsearch.gradle.test.RestIntegTestTask
 import org.elasticsearch.gradle.testclusters.TestClustersPlugin
 
 subprojects { Project subproj ->
-  subproj.tasks.withType(RestIntegTestTask).configureEach {
-    if (subproj.extensions.findByName("${it.name}Cluster")) {
-      subproj.extensions.configure("${it.name}Cluster") { cluster ->
-        cluster.distribution = System.getProperty('tests.distribution', 'oss')
-      }
-    }
-  }
   plugins.withType(TestClustersPlugin).whenPluginAdded {
     testClusters.all {
-      testDistribution = System.getProperty('tests.distribution', 'oss').toUpperCase()
+      testDistribution = 'DEFAULT'
     }
   }
 }