Don't create duplicated functions for code repositories and wiki repositories (#33924)

Fix
https://github.com/go-gitea/gitea/pull/33910#pullrequestreview-2688913865

This PR changed the Repositroy interface in `gitrepo` package which
makes it only focus the relative path in the disk and abstract whether
it's a wiki repository or not.

services/asymkey/sign.go

@@ -204,7 +204,7 @@ Loop:
 				return false, "", nil, &ErrWontSign{twofa}
 			}
 		case parentSigned:
-			gitRepo, err := gitrepo.OpenWikiRepository(ctx, repo)
+			gitRepo, err := gitrepo.OpenRepository(ctx, repo.WikiStorageRepo())
 			if err != nil {
 				return false, "", nil, err
 			}