Update to 1.21.2:

New Features:

• Add a target selection to the Screenshot Portal (#1981)
• Add pipewire-serials to ScreenCast Portal streams (#1942)

Enhancements:

• Provide proper errors when enabling autostart failed (#1906)
• Integration for the gobject-linter and respective fixes for rule violations (#1974, #1996)
• gvdb is now used as a meson subproject instead of a git subtree (#1978)
• Add a missing deprecation annotation to InputCapture.CreateSession (#1967)
• Various test and CI improvements (#1853, #1973, #1977)
• Various code cleanups (#1969, #1958, #1979, #1960)
• New and updated translations (#1965)

Bug Fixes:

• Improve how the document portal keeps track of granted documents to avoid access getting lost when the system is rebooted (#1950)
• Fix a regression which broke trashing files in Flatpak (#1982)
• Improvements to the handling of the impl and frontend portal versions (#1966, #1968, #1970)