chore(sensors_plus): Ignore BuildContext across async gaps warning in example (#3520)

Author: miquelbeltran

packages/sensors_plus/sensors_plus/example/lib/main.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// ignore_for_file: public_member_api_docs
+// ignore_for_file: public_member_api_docs, use_build_context_synchronously
 
 import 'dart:async';