docs: update branch model

Author: kenjis

contributing/pull_request.md

@@ -154,8 +154,9 @@ working on your contribution.
 
 ### Branching
 
-CodeIgniter4 uses the [Git-Flow](http://nvie.com/posts/a-successful-git-branching-model/) branching model
-which requires all Pull Requests to be sent to the __"develop"__ branch; this is where the next planned version will be developed.
+All bug fixes should be sent to the __"develop"__ branch, this is where the next bug fix version will be developed.
+
+PRs with any enhancement should be sent to __"4.3"__ branch, this is where the next minor upgrade version will be developed.
 
 The __"master"__ branch will always contain the latest stable version and is kept clean so a "hotfix" (e.g. an
 emergency security patch) can be applied to the "master" branch to create a new version, without worrying