Update github actions to newer versions

As per [0], we need to move to something newer than checkout@v2 in order
to avoid unsafe node versions.  This moves from checkout@v2 to
checkout@v4.

[0] https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#example-using-versioned-actions

Signed-off-by: Peter Jones <[email protected]>

.github/workflows/pullrequest.yml

@@ -76,7 +76,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           # otherwise we are testing target branch instead of the PR branch (see pull_request_target trigger)
           ref: ${{ github.event.pull_request.head.sha }}
@@ -150,7 +150,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           # otherwise we are testing target branch instead of the PR branch (see pull_request_target trigger)
           ref: ${{ github.event.pull_request.head.sha }}