Update personal and company information docs

What does this MR do and why?

Related to customers-gitlab-com#7008 (closed)

In preparation for [New CDot Nav][Feature flag] Roll out new_cdot_... (customers-gitlab-com#6372 - closed), update the account owner/company details documentation to support the new UI flow. Also updating GL account linking documentation to reference new Profile settings wording.

Screenshots or screen recordings

Before	After

header	header
Company information (includes tax ID when needed)
Profile settings (prev. Account details)
New menu dropdown UI

How to set up and validate locally

• Navigate to deployed documentation review app (link)
• To see the new CustomersPortal UI, navigate to https://customers.staging.gitlab.com/
  • The feature flag is currently default enabled in staging

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.