Quote Python version strings

GHA seemed to be interpreting 3.10 as 3.1?

Author: DomenicP

.github/workflows/build.yml

@@ -26,22 +26,22 @@ jobs:
         include:
           - name: "ubuntu-py27"
             os: ubuntu-latest
-            python-version: 2.7
+            python-version: "2.7"
           - name: "ubuntu-py37"
             os: ubuntu-latest
-            python-version: 3.7
+            python-version: "3.7"
           - name: "ubuntu-py38"
             os: ubuntu-latest
-            python-version: 3.8
+            python-version: "3.8"
           - name: "ubuntu-py39"
             os: ubuntu-latest
-            python-version: 3.9
+            python-version: "3.9"
           - name: "ubuntu-py310"
             os: ubuntu-latest
-            python-version: 3.10
+            python-version: "3.10"
           - name: "ubuntu-py311"
             os: ubuntu-latest
-            python-version: 3.11
+            python-version: "3.11"
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}