Actions: update to latest versions

Author: iMichka

.github/workflows/tests.yml

@@ -57,9 +57,9 @@ jobs:
             cppstd: "-std=c++98"
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v1
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Display Python version
@@ -89,7 +89,7 @@ jobs:
           coverage combine
           coverage xml
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v1
+        uses: codecov/codecov-action@v3
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           file: coverage.xml