Ignore upcoming unnecessary_imports analysis (#4023)

Author: srawlins

analysis_options.yaml

@@ -49,6 +49,8 @@ analyzer:
     # Allow null checks for as long as mixed mode is officially supported.
     unnecessary_null_comparison: false
     always_require_non_null_named_parameters: false # not needed with nnbd
+    # TODO(https://github.com/flutter/flutter/issues/74381)
+    unnecessary_imports: ignore
   exclude:
     # Ignore generated files
     - '**/*.g.dart'