python: Replace --mount with --wsgi-file
Replace the --mount /$TOOL=$HOME/www/python/src/app.py
directive with
--wsgi-file app.py
. The former config was needed with the legacy
tools.wmflabs.org/$TOOL hosting, but now only causes confusing bugs when
the deployed application uses routes with an initial path component that
exactly matches the value of $TOOL.
Bug: T337897