Workaround for macOS CI brew update error (#882)

Author: kyletsang

.github/workflows/ci.yml

@@ -23,7 +23,12 @@ jobs:
           node-version: 12.x
       - name: Update Brew (macOS)
         if: matrix.os == 'macOS-latest'
-        run: brew update
+        run: |
+          # Workaround https://github.com/actions/virtual-environments/issues/1811
+          brew untap local/homebrew-openssl
+          brew untap local/homebrew-python2
+          # End workaround
+          brew update
       - name: Install Chrome (macOS)
         if: matrix.os == 'macOS-latest' && matrix.browser == 'ChromeHeadless'
         run: brew cask install google-chrome