Revert "Temporarily run Windows tests via GitHub Actions (#3875)" (#3885)

diff --git a/.github/workflows/windows_ci.yml b/.github/workflows/windows_ci.yml
deleted file mode 100644
index 84aad92..0000000
--- a/.github/workflows/windows_ci.yml
+++ /dev/null
@@ -1,50 +0,0 @@
-name: CI
-
-on: [push, pull_request]
-
-jobs:
-  build_and_drive_windows:
-    runs-on: windows-2019
-    strategy:
-      matrix:
-        channel: ['master', 'stable']
-      # Disable fail-fast to get results from both channels even if one fails.
-      fail-fast: false
-
-    steps:
-    - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
-      with:
-        path: plugins
-    - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
-      with:
-        path: flutter
-        repository: flutter/flutter
-        ref: master
-        # Shallow clones don't work; see https://github.com/flutter/flutter/issues/18532
-        fetch-depth: 0
-    - name: Set up Flutter
-      run: |
-        # Add tags, which are also necessary for version checks to work.
-        git fetch origin +refs/tags/*:refs/tags/*
-        # Set channel
-        bin\flutter channel ${{matrix.channel}}
-        bin\flutter upgrade
-        # Enable desktop
-        bin\flutter config --enable-windows-desktop
-        # Add fluter to path.
-        echo "$env:GITHUB_WORKSPACE\flutter\bin" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
-      working-directory: ${{ github.workspace }}/flutter
-    - name: Doctor
-      # Run doctor, for ease of debugging any issues.
-      run: flutter doctor -v
-    - name: Set up tools
-      run: dart pub get
-      working-directory: ${{ github.workspace }}/plugins/script/tool
-    - name: Build
-      run: |
-        dart run ./script/tool/lib/src/main.dart build-examples --windows --run-on-changed-packages
-      working-directory: ${{ github.workspace }}/plugins
-    - name: Drive
-      run: |
-        dart run ./script/tool/lib/src/main.dart drive-examples --windows --run-on-changed-packages
-      working-directory: ${{ github.workspace }}/plugins
diff --git a/script/tool/lib/src/firebase_test_lab_command.dart b/script/tool/lib/src/firebase_test_lab_command.dart
index d4b8382..ff7d05b 100644
--- a/script/tool/lib/src/firebase_test_lab_command.dart
+++ b/script/tool/lib/src/firebase_test_lab_command.dart
@@ -27,8 +27,8 @@
       help: 'The Firebase project name.',
     );
     argParser.addOption('service-key',
-        defaultsTo: p.join(
-            io.Platform.environment['HOME'] ?? '/', 'gcloud-service-key.json'));
+        defaultsTo:
+            p.join(io.Platform.environment['HOME'], 'gcloud-service-key.json'));
     argParser.addOption('test-run-id',
         defaultsTo: Uuid().v4(),
         help: