Migrate build_info to null safety (#79469)

packages/flutter_tools/lib/src/build_system/targets/icon_tree_shaker.dart

@@ -22,9 +22,6 @@ import 'common.dart';
 /// only the glyphs used by the application.
 const String kIconTreeShakerFlag = 'TreeShakeIcons';
 
-/// Whether icon font subsetting is enabled by default.
-const bool kIconTreeShakerEnabledDefault = true;
-
 List<Map<String, dynamic>> _getList(dynamic object, String errorMessage) {
   if (object is List<dynamic>) {
     return object.cast<Map<String, dynamic>>();

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -19,7 +19,6 @@ import '../base/utils.dart';
 import '../build_info.dart';
 import '../build_system/build_system.dart';
 import '../build_system/targets/common.dart' show kExtraFrontEndOptions, kExtraGenSnapshotOptions; // for "useLegacyNames" only
-import '../build_system/targets/icon_tree_shaker.dart' show kIconTreeShakerEnabledDefault;
 import '../bundle.dart' as bundle;
 import '../cache.dart';
 import '../dart/generate_synthetic_packages.dart';