hgweb: don't use raw string for session vars
This r'' is leaking into the templating layer and causing an
assertion failure.
The r'' was added in d1fccbd50fcd (October 2017). Similar code
in hgweb_mod.py was also changed in that changeset. hgweb_mod.py was
updated in ec46415ed826 (March 2018) to use webutil.sessionvars(),
which doesn't use raw strings.
Differential Revision: https://phab.mercurial-scm.org/D5651
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.