Use correct boolean type in updateMany() example code

Author: jmikola

docs/reference/method/MongoDBCollection-updateMany.txt

@@ -61,7 +61,7 @@ The following example updates all of the documents with the ``borough`` of
 
    $updateResult = $collection->updateMany(
        [ 'borough' => 'Queens' ],
-       [ '$set' => [ 'active' => 'True' ]]
+       [ '$set' => [ 'active' => true ]]
    );
 
    printf("Matched %d document(s)\n", $updateResult->getMatchedCount());