Bump version to v4.2.2

[ClearlyClaire]

Changed

• Change dismissed banners to be stored server-side (ClearlyClaire)
• Change GIF max matrix size error to explicitly mention GIF files (ClearlyClaire)
• Change Follow activities delivery to bypass availability check (ShadowJonathan)
• Change single-column navigation notice to be displayed outside of the logo container (renchap, renchap)
• Change Content-Security-Policy to be tighter on media paths (ClearlyClaire)
• Change post language code to include country code when relevant (gunchleoc, ClearlyClaire)

Fixed

• Fix upper border radius of onboarding columns (ClearlyClaire)
• Fix incoming status creation date not being restricted to standard ISO8601 (ClearlyClaire, ClearlyClaire)
• Fix some posts from threads received out-of-order sometimes not being inserted into timelines (ClearlyClaire)
• Fix posts from force-sensitized accounts being able to trend (ClearlyClaire)
• Fix error when trying to delete already-deleted file with OpenStack Swift (ClearlyClaire)
• Fix batch attachment deletion when using OpenStack Swift (ClearlyClaire)
• Fix processing LDSigned activities from actors with unknown public keys (ClearlyClaire)
• Fix error and incorrect URLs in /api/v1/accounts/:id/featured_tags for remote accounts (ClearlyClaire)
• Fix report processing notice not mentioning the report number when performing a custom action (ClearlyClaire)
• Fix handling of inLanguage attribute in preview card processing (ClearlyClaire)
• Fix own posts being removed from home timeline when unfollowing a used hashtag (kmycode)
• Fix some link anchors being recognized as hashtags (ClearlyClaire, ClearlyClaire)
• Fix format-dependent redirects being cached regardless of requested format (ClearlyClaire)