github workflows: upgrade setup-python to version 4

Not much changes, really, other than it now sets PKG_CONFIG_PATH to
point to the python it just installed. This should generally not be a
problem (Meson's python module sets that anyway based on the
executable's introspection data).

.github/workflows/file_format.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
     - run: python3 ./run_format_tests.py

.github/workflows/lint.yml

@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
     - run: python -m pip install pylint
@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v4
         with:
           python-version: '3.x'
       - run: python -m pip install flake8
@@ -43,7 +43,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
     - run: python -m pip install mypy types-PyYAML

.github/workflows/macos.yml

@@ -28,7 +28,7 @@ jobs:
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
     - run: |
@@ -101,7 +101,7 @@ jobs:
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
     - run: python -m pip install -e .

.github/workflows/unusedargs_missingreturn.yml

@@ -45,7 +45,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
     - name: Install Compilers
@@ -63,7 +63,7 @@ jobs:
     runs-on: windows-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'