CI: don't fetch the whole git history if it's not required (#9021)

## Problem
We do use `actions/checkout` with `fetch-depth: 0` when it's not
required

## Summary of changes
- Remove unneeded `fetch-depth: 0`
- Add a comment if `fetch-depth: 0` is required

.github/workflows/trigger-e2e-tests.yml

@@ -34,8 +34,8 @@ jobs:
       build-tag: ${{ steps.build-tag.outputs.tag }}
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      # Need `fetch-depth: 0` to count the number of commits in the branch
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0