Upgrade GH actions to use Node 20 features instead of 16 (#48)

GH Actions have deprecated the use of Node 16, since it has reached
the end of its lifetime. Consequently, the outdated actions should
be upgraded. In case of Picire, the checkout and setup-python
actions need to be updated (v4 for checkout and v5 for
setup-python).

.github/workflows/main.yml

@@ -9,10 +9,10 @@ jobs:
         python-version: [3.8, 3.9, '3.10', '3.11', '3.12', 'pypy-3.9']
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - uses: actions/setup-python@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
       - run: pip install --upgrade tox
@@ -21,10 +21,10 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - uses: actions/setup-python@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: '3.x'
       - run: pip install --upgrade tox
@@ -33,10 +33,10 @@ jobs:
   cov:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - uses: actions/setup-python@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: '3.x'
       - run: pip install --upgrade tox coveralls
@@ -49,10 +49,10 @@ jobs:
     needs: [test, lint]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - uses: actions/setup-python@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: '3.x'
       - run: pip install --upgrade tox