Update the test workflow. (#118)

1.  Remove Python 2.7 and 3.6 (they are no longer supported)
2.  Add Python 3.11.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

Author: clalancette

.github/workflows/test.yml

@@ -14,11 +14,11 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: ['2.7', '3.6', '3.7', '3.8', '3.9', '3.10']
+        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
 
     steps:
     - name: Checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         lfs: 'true'