Remove line about nightlies in transformer building blocks tutorial (pytorch#3271)

Author: mikaylagawarecki

intermediate_source/transformer_building_blocks.py

@@ -3,8 +3,6 @@
 =============================================================================================================
 **Author:** `Mikayla Gawarecki <https://github.com/mikaylagawarecki>`_
 
-.. note::
-    This tutorial currently requires you to use the PyTorch nightly build.
 
 .. grid:: 2