Keep zola at 0.22.1, in step with the flake

zola 0.23 changes config.toml ([markdown.highlighting] no longer takes
`enabled`) and moved its binary in the image, while the flake that
runs the tests and local serve still has 0.22.1. Bumping only the
image split the two and broke the build (runs 411, 412). Go back to
0.22.1 and have Renovate leave the image pin alone: bump both together
by hand, with the config migration.

Assisted-by: Claude:opus-5-5

renovate.json

@@ -2,5 +2,14 @@
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
     "local>asxpi/renovate"
+  ],
+  "packageRules": [
+    {
+      "description": "zola must match the flake's (tests, local serve): bump both by hand, and migrate config.toml for 0.23 ([markdown.highlighting] lost `enabled`)",
+      "matchPackageNames": [
+        "ghcr.io/getzola/zola"
+      ],
+      "enabled": false
+    }
   ]
 }