Replace master branch with trunk in the Core handbook instructions for contributing with Git

[shooper]

In instructions on the ​The Code Repository (Git) reference using the master branch as your starting point.

Looking at the contents of the ​Git repo, that branch hasn't been updated since 2021.

It appears that the trunk branch is the actively maintained one.

Would suggest that references to master be replaced with trunk.

[JeffPaul]

Nice catch @shooper, any chance you can search the handbook to see if any other references need to similarly be updated so we can get them all at once?

[shooper]

Thanks @JeffPaul.

Found two more handbooks that reference master instead of trunk.

The Mobile apps handbook:
​https://make.wordpress.org/mobile/handbook/general-guides/git-branching/

The Meta contributing handbook:
​https://make.wordpress.org/meta/handbook/tutorials-guides/contributing-with-git/

[dd32]

Updated master to trunk on these pages:

• ​https://make.wordpress.org/mobile/handbook/general-guides/git-branching/
• ​https://make.wordpress.org/meta/handbook/tutorials-guides/contributing-with-git/
• ​https://make.wordpress.org/core/handbook/contribute/git/

I'll follow up with the mobile team as I think the reference to develop is outdated in their handbook.