fix(test): add trailing newline when no test folder found (#405)

Author: felangel

lib/src/cli/flutter_cli.dart

@@ -145,7 +145,7 @@ class Flutter {
 
         if (!Directory(p.join(target.dir.absolute.path, 'test')).existsSync()) {
           stdout?.call(
-            'No test folder found in ${target.dir.absolute.path}',
+            'No test folder found in ${target.dir.absolute.path}\n',
           );
           return ExitCode.success.code;
         }

test/src/cli/flutter_cli_test.dart

@@ -368,7 +368,7 @@ void main() {
           () => logger.write(
             any(
               that: contains(
-                'No test folder found in ${directory.path}',
+                'No test folder found in ${directory.path}\n',
               ),
             ),
           ),