Add quotes to Gradle NDK version error message (#109026)

Author: dcharkes

packages/flutter_tools/gradle/flutter.gradle

@@ -482,7 +482,7 @@ class FlutterPlugin implements Plugin<Project> {
                             project.logger.error("One or more plugins require a higher Android SDK version.\nFix this issue by adding the following to ${project.projectDir}${File.separator}build.gradle:\nandroid {\n  compileSdkVersion ${maxPluginCompileSdkVersion}\n  ...\n}\n")
                         }
                         if (maxPluginNdkVersion != projectNdkVersion) {
-                            project.logger.error("One or more plugins require a higher Android NDK version.\nFix this issue by adding the following to ${project.projectDir}${File.separator}build.gradle:\nandroid {\n  ndkVersion ${maxPluginNdkVersion}\n  ...\n}\n")
+                            project.logger.error("One or more plugins require a higher Android NDK version.\nFix this issue by adding the following to ${project.projectDir}${File.separator}build.gradle:\nandroid {\n  ndkVersion \"${maxPluginNdkVersion}\"\n  ...\n}\n")
                         }
                     }
                 }

packages/flutter_tools/test/integration.shard/android_plugin_ndkversion_mismatch_test.dart

@@ -77,7 +77,7 @@ void main() {
 One or more plugins require a higher Android NDK version.
 Fix this issue by adding the following to ${projectGradleFile.path}:
 android {
-  ndkVersion 21.4.7075529
+  ndkVersion "21.4.7075529"
   ...
 }