fix typo in comments to mention settings.gradle/.kts instead of build.gradle/.kts (flutter#175486)

fix typo above function that have mentions `build.gradle/.kts` while the
function returns `settings.gradle/.kts` file

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Author: AbdeMohlbi

packages/flutter_tools/lib/src/project.dart

@@ -599,8 +599,8 @@ class AndroidProject extends FlutterProjectPlatform {
 
   /// Gets the project root level Gradle settings file.
   ///
-  /// The file must exist and it must be written in either Groovy (build.gradle)
-  /// or Kotlin (build.gradle.kts).
+  /// The file must exist and it must be written in either Groovy (settings.gradle)
+  /// or Kotlin (settings.gradle.kts).
   File get settingsGradleFile {
     return getGroovyOrKotlin(hostAppGradleRoot, 'settings.gradle');
   }