ci: update versions of GitHub actions used in CI

Author: striezel

.github/workflows/build-clang.yml

@@ -10,7 +10,7 @@ jobs:
         version: [8, 9, 10, 11]
     steps:
       # Checks-out the repository under $GITHUB_WORKSPACE.
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Debian packages
         run: |
           sudo apt-get update

.github/workflows/build-gcc.yml

@@ -10,7 +10,7 @@ jobs:
         version: [8, 9, 10, 11]
     steps:
       # Checks-out the repository under $GITHUB_WORKSPACE.
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Debian packages
         run: |
           sudo apt-get update