sessionsaver: Add an explicit gi.require_version() for Tepl
The sessionsaver plugin is dumping a PyGIWarning into the journal at each launch (wrapped for readability):
/usr/lib64/gedit/plugins/sessionsaver/windowactivable.py:20:
PyGIWarning: Tepl was imported without specifying a version first.
Use gi.require_version('Tepl', '6') before import
to ensure that the right version gets loaded.
To avoid this, explicitly call gi.require_version('Tepl', '6')
in the __init__.py
.