docs: Remove sections about account management

Description

Redacts more text and images from the repo. gitlab!173182 (merged) moves this information into the gitlab repo:

• Account management
• How the account and project are selected
• Change the selected project and account

Related Issues

• Related to Plan for migrating VS Code user documentation (#1530 - closed)
• Depends on Migrate account-related subheadings (gitlab!173182 - merged) which moves this info into the gitlab repo
• Enables docs: Cut and reshuffle features section (!2149 - merged) which is the next round of work

How has this been tested?

Screenshots (if appropriate)

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes