unnecessary escapes fixes (#50178)

* unnecessary escapes fixes

* replace some strings with raw strings

* update regexp

* address review comments

packages/flutter_tools/lib/src/project.dart

diff --git a/packages/flutter_tools/lib/src/project.dart b/packages/flutter_tools/lib/src/project.dart
index 30cec47..2d01fcc 100644
--- a/packages/flutter_tools/lib/src/project.dart
+++ b/packages/flutter_tools/lib/src/project.dart
@@ -603,7 +603,7 @@
   String get pluginConfigKey => AndroidPlugin.kConfigKey;
 
   static final RegExp _applicationIdPattern = RegExp('^\\s*applicationId\\s+[\'"](.*)[\'"]\\s*\$');
-  static final RegExp _kotlinPluginPattern = RegExp('^\\s*apply plugin\:\\s+[\'"]kotlin-android[\'"]\\s*\$');
+  static final RegExp _kotlinPluginPattern = RegExp('^\\s*apply plugin\\:\\s+[\'"]kotlin-android[\'"]\\s*\$');
   static final RegExp _groupPattern = RegExp('^\\s*group\\s+[\'"](.*)[\'"]\\s*\$');
 
   /// The Gradle root directory of the Android host app. This is the directory