ci: customize Renovate PR title template option

Author: martin-georgiev

.github/renovate.json

@@ -21,7 +21,7 @@
     "minimumReleaseAge": "3 days",
     "stabilityDays": 3,
     "platformAutomerge": true,
-    "prTitle": "chore: ${depName} update",
+    "prTitle": "chore: {{depName}} update",
     "rangeStrategy": "auto",
     "rebaseWhen": "conflicted",
     "recreateWhen": "never",