Run CI against python 3.9 (#849)

Summary: Pull Request resolved: #849

Reviewed By: danielrjiang

Differential Revision: D29403826

Pulled By: Balandat

fbshipit-source-id: e9c5c7da3337da4a19a9db1bd8aac39f4ab782ac

Author: Balandat

.github/workflows/test.yml

@@ -17,7 +17,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: [3.7, 3.8]
+        python-version: [3.7, 3.8, 3.9]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}
@@ -44,7 +44,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: ["3.7", "3.8"]
+        python-version: ["3.7", "3.8", "3.9"]
     steps:
     - uses: actions/checkout@v2
     - uses: conda-incubator/setup-miniconda@v2