Branch 4.0 should be renamed branch 3.1

[Joberrr]

Hi There,

The Branch 4.0 should be renamed branch 3.1 or if it's to remain branch 4.0 we need to update the content to match master content.
I've tried to do this with git gui but not having any luck.
If anyone knows how to do this, most grateful if you can update it.