Account for updated Impeller label. (flutter#43450)

The label was updated per flutter.dev/go/triage-2023-rfc

Author: chinmaygarde

.github/labeler.yml

@@ -6,7 +6,7 @@
 embedder:
   - shell/platform/embedder
 
-impeller:
+'e: impeller':
   - impeller/**/*
 
 platform-android: