CI: Fix YAML screwup

Stupid number formats.

Signed-off-by: Stephen Finucane <stephen@that.guru>

Author: stephenfin

.github/workflows/ci.yaml

@@ -15,7 +15,7 @@ jobs:
       - name: Set up Python 3.10
         uses: actions/setup-python@v2
         with:
-          python-version: 3.10
+          python-version: '3.10'
       - name: Install dependencies
         run: python -m pip install tox
       - name: Run tox
@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: [3.7, 3.8, 3.9, 3.10]
+        python: ['3.7', '3.8', '3.9', '3.10']
     steps:
       - name: Checkout source code
         uses: actions/checkout@v2
@@ -49,7 +49,7 @@ jobs:
       - name: Set up Python 3.10
         uses: actions/setup-python@v2
         with:
-          python-version: 3.10
+          python-version: '3.10'
       - name: Install dependencies
         run: python -m pip install tox
       - name: Build docs (via tox)
@@ -73,7 +73,7 @@ jobs:
       - name: Set up Python 3.10
         uses: actions/setup-python@v2
         with:
-          python-version: 3.10
+          python-version: '3.10'
       - name: Install dependencies
         run: python -m pip install build
       - name: Build a binary wheel and a source tarball