backstage release v2.89.0-rc.2

Added

• (agent-platform) Render files attached to a session’s messages in #2459 by @QuentinBisson
• (gs) Read the Installations page’s versions in one request in #2721 by @teemow

Full Changelog: https://github.com/giantswarm/backstage/compare/v2.88.0...v2.89.0-rc.2