Airtable docs updates

[lauriemerrell]

Description

Describe your changes and why you're making them. Please include the context, motivation, and relevant dependencies.

This PR:

• Updates the Airtable documentation page to:
  • Delete outdated information (especially about the transit data assessments base, which as I understand it is deprecated)
  • Add information about considerations associated with ingesting Airtable data into the data warehouse
• Rearranges docs navigation:
  • Moves the "navigating the dbt docs" page into the warehouse section and removes the "legacy documentation" section
  • Moves the Transit Database (Airtable) specific docs into the developer section

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation

How has this been tested?

Include commands/logs/screenshots as relevant.

N/A - inspected preview link

Post-merge follow-ups

Document any actions that must be taken post-merge to deploy or otherwise implement the changes in this PR (for example, running a full refresh of some incremental model in dbt). If these actions will take more than a few hours after the merge or if they will be completed by someone other than the PR author, please create a dedicated follow-up issue and link it here to track resolution.

• No action required
• Actions required (specified below)

[github-actions]

Preview url: https://docs-data-infra-2868--cal-itp-previews.netlify.app

[SorenSpicknall]

Generally happy with this, so tentatively approving - just one note on a linked reference

[lauriemerrell]

Evan confirmed in Slack this is ok to merge!