updated Flutter Doctor grammar (#19676)

* updated Flutter Doctor grammar

* updated messaging based on a suggestion by Greg Spencer

* grammar update

packages/flutter_tools/lib/src/android/android_workflow.dart

@@ -94,7 +94,8 @@ class AndroidValidator extends DoctorValidator {
           'Install Android Studio from: https://developer.android.com/studio/index.html\n'
           'On first launch it will assist you in installing the Android SDK components.\n'
           '(or visit https://flutter.io/setup/#android-setup for detailed instructions).\n'
-          'If Android SDK has been installed to a custom location, set \$$kAndroidHome to that location.'
+          'If Android SDK has been installed to a custom location, set \$$kAndroidHome to that location.\n'
+          'You may also want to add it to your PATH environment variable.\n'
         ));
       }