git_remote_helpers: remove little used Python library

git_remote_helpers: remove little used Python library

When it was originally added, the git_remote_helpers library was used as
part of the tests of the remote-helper interface, but since commit
fc407f9 (Add new simplified git-remote-testgit, 2012-11-28) a simple
shell script is used for this.

A search on Ohloh [1] indicates that this library isn't used by any
external projects and even the Python remote helpers in contrib/ don't
use this library, so it is only used by its own test suite.

Since this is the only Python library in Git, removing it will make
packaging easier as the Python scripts only need to be installed for one
version of Python, whereas the library should be installed for all
available versions.

[1] http://code.ohloh.net/search?s=%22git_remote_helpers%22

Signed-off-by: John Keeping <john@keeping.me.uk>
Acked-by: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>