Clean up a few "%Q" stragglers in SVN repository browsing code

Summary: See https://discourse.phabricator-community.org/t/unsafe-raw-string-warning-for-svn-in-diffusion/2469.

Test Plan: Browed a Subversion repository in Diffusion. These are all reachable from the main landing page if the repository has commits/files, I think. Before change: errors in log; after change: no issues.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20244