fix some bad indentations (#41172)

diff --git a/packages/flutter_tools/lib/src/mdns_discovery.dart b/packages/flutter_tools/lib/src/mdns_discovery.dart
index 72aa60a..23c15fe 100644
--- a/packages/flutter_tools/lib/src/mdns_discovery.dart
+++ b/packages/flutter_tools/lib/src/mdns_discovery.dart
@@ -85,7 +85,7 @@
         buffer.writeln('There are multiple observatory ports available.');
         buffer.writeln('Rerun this command with one of the following passed in as the appId:');
         buffer.writeln('');
-         for (final String uniqueDomainName in uniqueDomainNames) {
+        for (final String uniqueDomainName in uniqueDomainNames) {
           buffer.writeln('  flutter attach --app-id ${uniqueDomainName.replaceAll('.$dartObservatoryName', '')}');
         }
         throwToolExit(buffer.toString());