ci: Make Ubuntu versions explicit

Github just migrated us to Ubuntu 22.04, but it can't run Python 3.6 on it

.github/workflows/test.yml

@@ -10,15 +10,45 @@ jobs:
     runs-on: ${{ matrix.runs-on }}
     strategy:
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11.0-rc.2", "pypy-3.6", "pypy-3.7"]
+        include:
-        with-opt-deps: [false, true]
+          - python-version: "3.11.0-rc.2"
-        runs-on: [ubuntu-latest]
+            with-opt-deps: true
-        exclude:
+            runs-on: ubuntu-22.04
-          # Some of the dependencies don't work on old Python versions
+
+          - python-version: "3.10"
+            with-opt-deps: true
+            runs-on: ubuntu-22.04
+          - python-version: "3.10"
+            with-opt-deps: false
+            runs-on: ubuntu-22.04
+
+          - python-version: "3.9"
+            with-opt-deps: true
+            runs-on: ubuntu-22.04
+
+          - python-version: "3.8"
+            with-opt-deps: true
+            runs-on: ubuntu-22.04
+
+          - python-version: "3.7"
+            with-opt-deps: true
+            runs-on: ubuntu-22.04
+          - python-version: "3.7"
+            with-opt-deps: false
+            runs-on: ubuntu-22.04
+          - python-version: "pypy-3.7"
+            with-opt-deps: true
+            runs-on: ubuntu-22.04
+          - python-version: "pypy-3.7"
+            with-opt-deps: false
+            runs-on: ubuntu-22.04
+
           - python-version: "3.6"
-            with-opt-deps: true
+            with-opt-deps: false
+            runs-on: ubuntu-20.04
           - python-version: "pypy-3.6"
-            with-opt-deps: true
+            with-opt-deps: false
+            runs-on: ubuntu-20.04
 
     steps:
       - uses: actions/checkout@v2