PHPLIB-461: Fix ChangeStream tests on sharded clusters

tests/DocumentationExamplesTest.php

@@ -935,6 +935,10 @@ class DocumentationExamplesTest extends FunctionalTestCase
     {
         $this->skipIfChangeStreamIsNotSupported();
 
+        if ($this->isShardedCluster()) {
+            $this->markTestSkipped('Test does not apply on sharded clusters: need more than a single getMore call on the change stream.');
+        }
+
         $db = new Database($this->manager, $this->getDatabaseName());
         $db->dropCollection('inventory');
         $db->createCollection('inventory');

tests/FunctionalTestCase.php

@@ -336,9 +336,6 @@ abstract class FunctionalTestCase extends TestCase
                 if (! $this->isShardedClusterUsingReplicasets()) {
                     $this->markTestSkipped('$changeStream is only supported with replicasets');
                 }
-
-                // Temporarily skip tests because of an issue with change streams in the driver
-                $this->markTestSkipped('$changeStreams currently don\'t on replica sets');
                 break;
 
             case Server::TYPE_RS_PRIMARY: