fix(forgejo): bump chart targetRevision 13.1.0 -> 17.0.1 (#29)

Chart version 13.1.0 doesn't exist in the OCI registry; ArgoCD's
repo-server failed with `code.forgejo.org/forgejo-helm/forgejo:13.1.0:
not found`. Latest is 17.0.1 — switch to it.
`gitea.oauth[].existingSecret` is still the supported API in this
version, so no values changes needed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: xnoto

operators/forgejo/application.yaml

@@ -14,7 +14,7 @@ spec:
   source:
     chart: forgejo
     repoURL: code.forgejo.org/forgejo-helm
-    targetRevision: 13.1.0
+    targetRevision: 17.0.1
     helm:
       releaseName: forgejo
       valuesObject: