Merge pull request #316 from pestphp/bugfix/phpunit-12-references

docs: resolve incorrect references to PHPUnit 12

Author: nunomaduro

upgrade-guide.md

@@ -1,6 +1,6 @@
 ---
 title: Upgrade Guide
-description: Upgrading To 3.x From 2.x
+description: Upgrading To 4.x From 3.x
 ---
 
 ## Upgrading To 4.x From 3.x