prettier: avoid creating empty node_modules/.cache

prettier resolves its cache location by default to a file under
node_modules/.cache/prettier. And even when prettier cache is
disabled (by default) the directory for storing the cache file is still
created.

This commit removes the creation of that empty directory when formatting
files using the fix:format:prettier task.

package.json

@@ -4,7 +4,7 @@
     "check:npm:dedupe": "npm find-dupes",
     "check:prettier": "prettier --check .",
     "check:renovateconfig": "npx --package=renovate -- renovate-config-validator --strict",
-    "fix:prettier": "prettier --write ."
+    "fix:prettier": "prettier --write --cache-location .prettiercache ."
   },
   "private": true,
   "engines": {