Update git master to git main in tutorial

[comaraDOTcom]

Just noticed that the git push should push to the main branch of a new repo now as references to a master branch are no longer used by Github.

Description & motivation

I was going through the tutorial and noticed there is a reference to

$ git push -u origin master

which could be confusing to people who are new to git since git now uses main instead of master. I propose we change it to the following.

$ git push -u origin main

To-do before merge

Pre-release docs

Is this change related to an unreleased version of dbt?

• Yes: please
  • update the base branch to next
  • add Changelog components: <Changelog>[New/Changed] in v0.x.0</Changelog>
  • add links to the "New and changed documentation" section of the latest Migration Guide
• No: please ensure the base branch is current
• Unsure: we'll let you know!

Checklist

If you added new pages (delete if not applicable):

• The page has been added to website/sidebars.js
• The new page has a unique filename

If you removed existing pages (delete if not applicable):

• The page has been removed from website/sidebars.js
• An entry has been added to _redirects

[VersusFacit]

Thanks a lot for spotting this.