[ci] Re-enable all Android legacy emulator tests (#10141)

Now that the legacy emulators are API 31, not 22, these exclusions are stale.

Fixes flutter/flutter#136824
Fixes flutter/flutter#136823

Author: stuartmorgan-g

script/configs/exclude_integration_android_legacy_emulator.yaml

@@ -1,13 +1,3 @@
-# This plugin no-ops below API 25, which is newer than the legacy emulator.
-# This can be removed once the legacy emulator test is using at least
-# API level 25.
-- quick_actions
-- quick_actions_android
-# Fails on the legacy emulator. See https://github.com/flutter/flutter/issues/136823
-# TODO(stuartmorgan): Remove this if the limitation can be worked around.
-- video_player
-- video_player_android
-# Hangs on the legacy emulator. See https://github.com/flutter/flutter/issues/136824
-# TODO(stuartmorgan): Remove this if the hang can be fixed.
-- webview_flutter
-- webview_flutter_android
+# Currently no plugins need to be excluded, but this file is left
+# since it is likely that we will need this functionality in the future.
+[]