Revert "THRIFT-5567: remove cl namespace references (#2580)"

This reverts commit 45471decdf572156189e66db59c8a1e82085299f.
diff --git a/tutorial/tutorial.thrift b/tutorial/tutorial.thrift
index 6e33130..f1e2912 100644
--- a/tutorial/tutorial.thrift
+++ b/tutorial/tutorial.thrift
@@ -63,6 +63,7 @@
  * target languages.
  */
 
+namespace cl tutorial
 namespace cpp tutorial
 namespace d tutorial
 namespace dart tutorial