Merge pull request #336 from OpenPrinting/dependabot/github_actions/actions/checkout-4.1.0

Bump actions/checkout from 3.6.0 to 4.1.0

Author: zdohnal

.github/workflows/differential-shellcheck.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps: 
       - name: Repository checkout
-        uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744
+        uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608
         with:
           fetch-depth: 0