Pin checkout at v3 in all workflows

This fixes some CI warnings about using obsolete versions of NodeJS.
NodeJS 12 (from checkout@2) is at EOL, and CI warnings recommend using
NodeJS 16. The docs for actions/checkout recommend pinning at v3.

Some of these workflows were using `checkout@master`, and were thereby
already using NodeJS 16. I'm not sure that it's necessary to use v3
for these instead of master. However, the docs suggest using v3.
If at some point the authors decide to rename the `master` branch to
`main`, then we may be glad we made this change.

.github/workflows/check-combinations.yml

@@ -14,7 +14,7 @@ jobs:
   check_combinations:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
       with:
         fetch-depth: 20
       

.github/workflows/check.yml

@@ -16,7 +16,7 @@ jobs:
     name: Check packaging 📦
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
       with:
         fetch-depth: 20
     - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*

.github/workflows/codeql-analysis.yml

@@ -28,7 +28,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v2

.github/workflows/publish-to-pypi.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: Checkout 🛎️
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           fetch-depth: 50
       - name: Fetch release tag

.github/workflows/release-note.yml

@@ -7,7 +7,7 @@ jobs:
   create-release-notes:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
     - name: Create Release Notes
       uses: docker://decathlon/release-notes-generator-action:2.0.0
       env:

.github/workflows/test-install-qt.yml

@@ -25,7 +25,7 @@ jobs:
             py: "3.10"
             qtver: 6.1.0
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v3
         with:
           fetch-depth: 20
       - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*

.github/workflows/upload-release-artifacts.yml

@@ -19,7 +19,7 @@ jobs:
         py: [3.9]
         arch: [x86, x64]
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v3
         with:
           fetch-depth: 20
       - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*