[py] use bash syntax

Author: cgoldberg

.github/workflows/ci-python.yml

@@ -71,8 +71,9 @@ jobs:
       name: Unit Tests (${{ matrix.os }})
       os: ${{ matrix.os }}
       cache-key: python-unit-test-${{ matrix.os }}
+      shell: bash
       run: |
-        if [[ "${{ runner.os }}" == "Windows" ]]; then
+        if [ "$RUNNER_OS" == "Windows" ]; then
           fsutil 8dot3name set 0
         fi
         bazel test //py:unit
@@ -118,8 +119,9 @@ jobs:
       browser: ${{ matrix.browser }}
       os: ${{ matrix.os }}
       cache-key: py-browser-${{ matrix.browser }}
+      shell: bash
       run: |
-        if [[ "${{ runner.os }}" == "Windows" ]]; then
+        if [ "$RUNNER_OS" == "Windows" ]; then
           fsutil 8dot3name set 0
         fi
         bazel test --local_test_jobs 1 --flaky_test_attempts 3 --pin_browsers=true //py:common-${{ matrix.browser }}-bidi //py:test-${{ matrix.browser }}