renovate: fix ignorePaths

the intent is to ignore `Dockerfile` while still providing updates to
`Dockerfile.base`, but this was not working and renovate was ignoring
both

in my local testing this seems to have fixed that issue

Author: joemiller

renovate.json

@@ -5,7 +5,7 @@
     "github>planetscale/renovate-config:weeklyBatchMinorPatchDigest"
   ],
   "ignorePaths": [
-    "Dockerfile"
+    "**/Dockerfile"
   ],
   "packageRules": [
     {