Removed Python 3.6 from CI

.github/workflows/build.yml

@@ -13,10 +13,10 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v1
-      - name: Set up Python 3.6
+      - name: Set up Python 3.7
         uses: actions/setup-python@v2
         with:
-          python-version: 3.6
+          python-version: 3.7
 
       - name: Install dependencies
         run: |
@@ -39,7 +39,7 @@ jobs:
     strategy:
       matrix:
         os: [windows-2019, ubuntu-20.04, macos-10.15]
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.7, 3.8]
 
     steps:
       - uses: actions/checkout@v1