Mark sysop parameter as deprecated

Gerrit Ib8df9866 makes bot can switch to sysop account to edit pages
by using parameter "as_group='sysop'". This replaces parameter
"sysop=True" in compat. This patch therefore marks the parameter
sysop as deprecated.

Bug: 58789
Change-Id: Ifccab04a63c8bc418ade7fafd795450a121e7c19
Merge "Mark sysop parameter as deprecated"