Update projects.md Removed duplicate "Project merge method" section

What does this MR do?

Corrects a documentation oversight, where there were two sections for "Project merge method"

Are there points in the code the reviewer needs to double check?

Just to confirm that the proposed removed section is 100% identical to the section that will remain.

Why was this MR needed?

No editing permissions to the master branch for the public, and this saves face - copy/paste oversight is awkward for users.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

Probably not, I didn't follow any of those things, nor are many of them relevant. Ex: Internationalization was certainly not considered.

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Maybe it would have been quicker to create an issue than to put in a merge request - feel free to close this one if that is preferred.