Update UPGRADING.md

Author: claudiodekker

UPGRADING.md

@@ -17,7 +17,7 @@ To update it and make it compatible with 2.x, all you need to do is add one line
 ```
 
 
-## 2.x -> 4.x
+## 2.x -> 5.x
 The color utilities provided by TailwindCSS [have changed since it's 1.0 release](https://tailwindcss.com/docs/upgrading-to-v1#1-update-any-usage-of-text-bg-border-color-classes), and [we've changed our alert template to reflect this](https://github.com/ubient/laravel-flash-message/commit/58b470b8933cd5be7914620fa1b22b2411a38e4b#diff-efa7508de9508f985738c4dbb5b6147b). If you're depending on the built-in alert template this package ships with, and you're still using the older version of TailwindCSS, you'll most likely want to [publish it](README.md#customizing-the-template) prior to upgrading this newer version. To do this, you may use the following command:
 
 ```bash