Release 3.9.0-rc2

What's Changed

• [stable-3.9] Fix tray window header folders button colour by @backportbot-nextcloud in nextcloud/desktop#5723
• [stable-3.9] align activity text with "Sync now" text by @backportbot-nextcloud in nextcloud/desktop#5725
• [stable-3.9] ensure that the file to test monitoring is hidden by @backportbot-nextcloud in nextcloud/desktop#5733
• [stable-3.9] Fix tray styling by @backportbot-nextcloud in nextcloud/desktop#5741

Full Changelog: nextcloud/desktop@v3.9.0-rc1...v3.9.0-rc2