Update project settings for circleci 2.0

[eddiewebb]

Noticed report in https://discuss.circleci.com/t/step-3-on-edit-project-settings-project-overview-needs-update/21245

Project settings is specific to 1.0. These edits remind users of pending retirement, and prioritize 2.0 instructions.

Rationale This PR addresses omission in Project Settings page that still uses circleci 1.0 links and references.

Considerations

• Page had no mention of the 1.0/2.0 distinctions or retirement.
• The page's "Option 3" is the only valid option moving forward, but links to old 1.0 docs
• Users are reporting bugs

Ticket: Discuss Bug Report

Before

After