fix msg

src/server/routes/apiv3/slack-integration-settings.js

@@ -512,7 +512,7 @@ module.exports = (crowi) => {
       // TODO impl return response after imple 5996, 6002
     }
     catch (error) {
-      const msg = 'Error occured in sending test message';
+      const msg = 'Error occured while sending a test message';
       logger.error('Error', error);
       return res.apiv3Err(new ErrorV3(msg, 'send-message-to-slack-failed'), 500);
     }