[ci] Update CI to use Reduced test plan

Author: nan-li

.github/workflows/ci.yml

@@ -40,10 +40,11 @@ jobs:
       - name: Test
         env:
           scheme: ${{ 'UnitTestApp' }}
+          test_plan: ${{ 'UnitTestApp_TestPlan_Reduced' }}
           platform: ${{ 'iOS Simulator' }}
           file_to_build: ${{ 'iOS_SDK/OneSignalSDK/OneSignal.xcodeproj' }}
           filetype_parameter: ${{ 'project' }}
         run: |
           # xcrun xctrace returns via stderr, not the expected stdout (see https://developer.apple.com/forums/thread/663959)
           device=`xcrun xctrace list devices 2>&1 | grep -oE 'iPhone.*?[^\(]+' | head -1 | awk '{$1=$1;print}' | sed -e "s/ Simulator$//"`
-          xcodebuild test-without-building -scheme "$scheme" -"$filetype_parameter" "$file_to_build" -destination "platform=$platform,name=$device"
+          xcodebuild test-without-building -scheme "$scheme" -testPlan "$test_plan" -"$filetype_parameter" "$file_to_build" -destination "platform=$platform,name=$device"