🚚 Unlock Weblate script should run as pull_request_target (#5466)

If not, it won't have access to secrets.

.github/workflows/unlock-weblate.yml

@@ -4,7 +4,7 @@
 # We do this to avoid conflicts.
 name: Unlock Weblate when PR is closed
 on:
-  pull_request:
+  pull_request_target:
     types:
       - closed