tests: remove obsolete PYTHONPATH override from remotefilelog tests They were added in https://bitbucket.org/facebook/hg-experimental/commits/fdcad37a6a68cfbaf5920f3eeaa0cc9cae42bd26, which says this: When remotefilelog moved from its own repo, the tests needed to be updated to adjust the PYTHONPATH to ensure the in-repo remotefilelog was loaded instead of the system one. This meant any local runs of remotefilelog tests would've been using the system remotefilelog unless the user had manually set the PYTHONPATH themselves. That doesn't seem relevant with remotefilelog in core. Differential Revision: https://phab.mercurial-scm.org/D5248