Non-i18n build should also reinstall plugins

Since we're caching the Lektor packages dir, we should reinitialise it
before starting the build, otherwise uninstalled or modified plugins may
not be taken into account.
1 job for !17 with reinstall-plugins in 16 seconds (queued for 2 seconds)
latest detached
Status Name Job ID Coverage
  Test
passed test #56176

00:00:16