fix(ci): where python is too old for ubuntu-latest, use earlier ubuntu

Author: chaimleib

.github/workflows/build.yml

@@ -14,12 +14,27 @@ permissions:
 
 jobs:
   build:
-
-    runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["2.7", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
-
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
+        include:
+          - python-version: "3.6"
+            os: ubuntu-20.04
+          - python-version: "3.7"
+            os: ubuntu-22.04
+          - python-version: "3.8"
+            os: ubuntu-24.04
+          - python-version: "3.9"
+            os: ubuntu-24.04
+          - python-version: "3.10"
+            os: ubuntu-24.04
+          - python-version: "3.11"
+            os: ubuntu-24.04
+          - python-version: "3.12"
+            os: ubuntu-24.04
+          - python-version: "3.13"
+            os: ubuntu-24.04
+    runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}