Tiny cleanup I noticed while trying to fix/test another issue
(https://github.com/syncthing/syncthing/pull/9600). I shortly tried to
figure out what it was used for in the past, but gave up without
results.
This solves the erratic test failures on model.TestIgnores by ensuring
that the ignore patterns are reloaded even in the face of unchanged
timestamps.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4208
