Update actions/checkout to v4 in lint workflow

Author: angristan

.github/workflows/lint.yml

@@ -6,7 +6,7 @@ jobs:
   shellcheck:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: shellcheck
         uses: ludeeus/[email protected]
         env:
@@ -15,6 +15,6 @@ jobs:
   shfmt:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: mfinelli/setup-shfmt@v3
       - run: shfmt -d wireguard-install.sh