Build: Stop double generating buildSrc pom (#32408)

When we added the `java-gradle-plugin` to `buildSrc` it added a second
task to generate the pom that duplicates the publishing work that we
configure in `BuildPlugin`. Not only does it dupliciate the pom, it
creates a pom that is missing things like `name` and `description` which
are required for publishing to maven central.

This change disables the duplicate pom generation.

buildSrc/build.gradle

@@ -183,4 +183,12 @@ if (project != rootProject) {
     testClass = 'org.elasticsearch.gradle.test.GradleUnitTestCase'
     integTestClass = 'org.elasticsearch.gradle.test.GradleIntegrationTestCase'
   }
+
+  /*
+   * We alread configure publication and we don't need or want this one that
+   * comes from the java-gradle-plugin.
+   */
+  afterEvaluate {
+    generatePomFileForPluginMavenPublication.enabled = false
+  }
 }