[setup.py] drop Py3.6 support

Author: chrissimpkins

.github/workflows/py-ci.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.7, 3.8, 3.9, 3.10]
 
     steps:
       - uses: actions/checkout@v2

setup.py

@@ -10,7 +10,7 @@
 URL = "https://github.com/source-foundry/fdiff"
 EMAIL = "chris@sourcefoundry.org"
 AUTHOR = "Source Foundry Authors"
-REQUIRES_PYTHON = ">=3.6.0"
+REQUIRES_PYTHON = ">=3.7.0"
 
 INSTALL_REQUIRES = [
     "fontTools >= 4.0.0",