gitea: drop the orphaned runner pvc that could never bind

gitea-runner-pvc referenced volumeName gitea-runner-data, but neither that
PV nor a Longhorn volume of that name exists, so it sat Pending since May.
ArgoCD treats a Pending PVC as Progressing and rolled that up to the whole
app, which is why gitea never reported Healthy.

Nothing mounted it. The runner uses the PVC the gitea/actions chart
generates from its own volumeClaimTemplate.

applications/gitea/runner/gitea-runner-persistentvolumeclaim.yaml

@@ -1,13 +0,0 @@
-apiVersion: v1
-kind: PersistentVolumeClaim
-metadata:
-  name: gitea-runner-pvc
-  namespace: gitea
-spec:
-  accessModes:
-    - ReadWriteOnce
-  storageClassName: longhorn-static
-  volumeName: gitea-runner-data
-  resources:
-    requests:
-      storage: 20Gi