Remove trailing comma in argument list

This was causing a test failure for PHP versions before 8.0

Author: jmikola

tests/SpecTests/ClientSideEncryptionSpecTest.php

@@ -1424,7 +1424,7 @@ public function testUniqueIndexOnKeyAltNames(Closure $test): void
                 'unique' => true,
                 'partialFilterExpression' => ['keyAltNames' => ['$exists' => true]],
                 'writeConcern' => new WriteConcern(WriteConcern::MAJORITY),
-            ],
+            ]
         );
 
         $clientEncryption = new ClientEncryption([