remove python3.6 test/lint support due to actions/setup-python#162

Author: MichaelHopwood

.github/workflows/lint-and-test.yml

@@ -7,11 +7,11 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.7, 3.8]
         requirements: [requirements.txt]
         include:
           - requirements: requirements-min.txt
-            python-version: 3.6
+            python-version: 3.7
             os: ubuntu-latest
 
     runs-on: ${{ matrix.os }}
@@ -35,7 +35,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.7, 3.8]
 
     runs-on: ubuntu-latest