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: I7bbbf8ab0f47c6f8a3b25e92e4678e76c77f19a1
Merge "remove unneeded definitions of Python Source Code Encoding"