remove cPy 3.5 testing, add cPy 3.9 testing

Author: chrissimpkins

.github/workflows/linuxci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8, pypy3]
+        python-version: [3.6, 3.7, 3.8, 3.9, pypy3]
     name: Linux CI
     steps:
       - name: Check out source repository

.github/workflows/macosci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8, pypy3]
+        python-version: [3.6, 3.7, 3.8, 3.9, pypy3]
     name: macOS CI
     steps:
       - name: Check out source repository

.github/workflows/windowsci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8, pypy3]
+        python-version: [3.6, 3.7, 3.8, 3.9, pypy3]
     name: Windows CI
     steps:
       - name: Check out source repository