ci: remove redundant actions/checkout steps from dev-infra workflows

Checking out the repo is not needed for these actions.

(cherry picked from commit 4d345b5)

Author: alan-agius4

.github/workflows/dev-infra.yml

@@ -15,15 +15,13 @@ jobs:
     if: github.event_name == 'pull_request_target'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: angular/dev-infra/github-actions/labeling/pull-request@63fd18d4726829e65f6abe6f15c0fe79f63f1dec
         with:
           angular-robot-key: ${{ secrets.ANGULAR_ROBOT_PRIVATE_KEY }}
   post_approval_changes:
     if: github.event_name == 'pull_request_target'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: angular/dev-infra/github-actions/post-approval-changes@63fd18d4726829e65f6abe6f15c0fe79f63f1dec
         with:
           angular-robot-key: ${{ secrets.ANGULAR_ROBOT_PRIVATE_KEY }}