Instruct Renovate to pin GitHub Action hashes (jaegertracing#6860)

## Which problem is this PR solving?
- In light of
https://semgrep.dev/blog/2025/popular-github-action-tj-actionschanged-files-is-compromised/,
make sure all actions are pinned

## Description of the changes
- Turns out Renovate has this as a feature
https://docs.renovatebot.com/modules/manager/github-actions/#digest-pinning-and-updating

## How was this change tested?
- CI

---------

Signed-off-by: Yuri Shkuro <[email protected]>

Author: yurishkuro

renovate.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
-    "config:recommended",
+    "config:best-practices",
     ":gitSignOff"
   ],
   "labels": [