What changes were proposed in this pull request?

This PR aims to update CIs to use actions/checkout@v4 consistently.

Why are the changes needed?

BEFORE

$ git grep actions/checkout | awk '{print $NF}' | sort | uniq -c
   1 actions/checkout@v3
  11 actions/checkout@v4

AFTER

$ git grep actions/checkout | awk '{print $NF}' | sort | uniq -c
  12 actions/checkout@v4

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Pass the CIs and manually check with git grep actions/checkout.

Was this patch authored or co-authored using generative AI tooling?

No.