Remove unneeded definitions of Python Source Code Encoding

I think PEP 0263 (http://legacy.python.org/dev/peps/pep-0263/) is
not used anywhere else and so it should be removed when it's not
needed.

Change-Id: I013bf7f1df485d79b4cf17b874bfb22a0b920f2b
Merge "Remove unneeded definitions of Python Source Code Encoding"