Reenable UnobstructedPlatformViewTests testMultiplePlatformViewsWithOverlays (flutter/engine#48139)

Renable test now that https://github.com/flutter/flutter/issues/138193 is fixed.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

engine/src/flutter/testing/scenario_app/run_ios_tests.sh

@@ -61,15 +61,12 @@ zip_and_upload_xcresult_to_luci () {
 echo "Running simulator tests with Skia"
 echo ""
 
-# TODO(vashworth): Stop skipping testMultiplePlatformViewsWithOverlays once
-# https://github.com/flutter/flutter/issues/138193 is resolved
 if set -o pipefail && xcodebuild -sdk iphonesimulator \
   -scheme Scenarios \
   -resultBundlePath "$RESULT_BUNDLE_PATH/ios_scenario.xcresult" \
   -destination 'platform=iOS Simulator,OS=16.2,name=iPhone SE (3rd generation)' \
   clean test \
-  FLUTTER_ENGINE="$FLUTTER_ENGINE" \
-  -skip-testing ScenariosUITests/UnobstructedPlatformViewTests/testMultiplePlatformViewsWithOverlays; then
+  FLUTTER_ENGINE="$FLUTTER_ENGINE"; then
   echo "test success."
 else
   echo "test failed."