[PURIFY] remove all trace of x-pack migration (#19)

This commit removes all trace of Elastic licensed Migration

buildSrc/src/main/resources/checkstyle_suppressions.xml

@@ -31,12 +31,8 @@
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]CRUDDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]IndicesClientDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]IngestClientDocumentationIT.java" id="SnippetLength" />
-  <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]LicensingDocumentationIT.java" id="SnippetLength" />
-  <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]MigrationDocumentationIT.java" id="SnippetLength" />
-  <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]MigrationClientDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]MiscellaneousDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]SearchDocumentationIT.java" id="SnippetLength" />
-  <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]SecurityDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]SnapshotClientDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]StoredScriptsDocumentationIT.java" id="SnippetLength" />
   <suppress files="client[/\\]rest-high-level[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]documentation[/\\]TasksClientDocumentationIT.java" id="SnippetLength" />

client/rest-high-level/src/main/java/org/elasticsearch/client/RestHighLevelClient.java

@@ -261,7 +261,6 @@ public class RestHighLevelClient implements Closeable {
     private final SnapshotClient snapshotClient = new SnapshotClient(this);
     private final TasksClient tasksClient = new TasksClient(this);
     private final WatcherClient watcherClient = new WatcherClient(this);
-    private final MigrationClient migrationClient = new MigrationClient(this);
     private final IndexLifecycleClient ilmClient = new IndexLifecycleClient(this);
     private final TransformClient transformClient = new TransformClient(this);
 
@@ -375,18 +374,6 @@ public IndexLifecycleClient indexLifecycle() {
         return ilmClient;
     }
 
-    /**
-     * Provides methods for accessing the Elastic Licensed Migration APIs that
-     * are shipped with the default distribution of Elasticsearch. All of
-     * these APIs will 404 if run against the OSS distribution of Elasticsearch.
-     * <p>
-     * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/migration-api.html">
-     * Migration APIs on elastic.co</a> for more information.
-     */
-    public MigrationClient migration() {
-        return migrationClient;
-    }
-
     /**
      * Provides methods for accessing the Elastic Licensed Data Frame APIs that
      * are shipped with the Elastic Stack distribution of Elasticsearch. All of