borg config repo ... does not need cache/manifest/key, fixes #3802

thus, we should not use the with_repository decorator to set up
the cache / key / manifest.

this enables running borg config on the repo without the key / key
passphrase (the config itself is in plaintext).

src/borg/archiver.py

@@ -1718,8 +1718,8 @@ class Archiver:
             # see issue #1867.
             repository.commit()
 
-    @with_repository(exclusive=True, cache=True, compatibility=(Manifest.Operation.WRITE,))
-    def do_config(self, args, repository, manifest, key, cache):
+    @with_repository(exclusive=True, manifest=False)
+    def do_config(self, args, repository):
         """get, set, and delete values in a repository or cache config file"""
 
         def repo_validate(section, name, value=None, check_value=True):