MPP-4193 Remove VPN Relay Banner

[vpremamozilla]

MPP-4193

Users no longer see the Relay+VPN promotion banner on the Relay Dashboard.

Screenshot (if applicable)

BEFORE

AFTER

How to test

• log into Relay
• banner should no longer appear

Checklist (Definition of Done)

• Product Owner accepted the User Story (demo of functionality completed) or waived the privilege.
• Customer Experience team has seen or waived a demo of functionality.
• All acceptance criteria are met.
• Jira ticket has been updated (if needed) to match changes made during the development process.
• I've added or updated relevant docs in the docs/ directory
• Jira ticket has been updated (if needed) with suggestions for QA when this PR is deployed to stage.
• All UI revisions follow the coding standards, and use Protocol / Nebula colors where applicable (see /frontend/src/styles/colors.scss).
• Commits in this PR are minimal and have descriptive commit messages.
• l10n changes have been submitted to the l10n repository, if any.

[groovecoder]

change (blocking): looks like we can remove the frontend/src/components/landing/images/vpn-and-relay-logo.svg and frontend/src/components/dashboard/images/vpn-and-relay-logo.svg files too.