Fixed typo (subetting -> subsetting) (#62502)

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

@@ -61,7 +61,7 @@ class IconTreeShaker {
        _fontManifest = fontManifest?.string {
     if (_environment.defines[kIconTreeShakerFlag] == 'true' &&
         _environment.defines[kBuildMode] == 'debug') {
-      logger.printError('Font subetting is not supported in debug mode. The '
+      logger.printError('Font subsetting is not supported in debug mode. The '
                          '--tree-shake-icons flag will be ignored.');
     }
   }

packages/flutter_tools/test/general.shard/build_system/targets/icon_tree_shaker_test.dart

@@ -138,7 +138,7 @@ void main() {
 
     expect(
       logger.errorText,
-      'Font subetting is not supported in debug mode. The --tree-shake-icons'
+      'Font subsetting is not supported in debug mode. The --tree-shake-icons'
       ' flag will be ignored.\n',
     );
     expect(iconTreeShaker.enabled, false);