some snaps reverting to Adwaita theme with newest versions of gtk-common-themes

[sktsee]

Some snaps apps (Firefox, Chromium, Snap-Store, Fluffychat, Gedit) change from Yaru (default theme) to Adwaita themeing after updating gtk-common-themes. This has occurred with the last two revisions, 1534 and 1535. Themeing of the above listed apps correctly work with revision 1519 (0.1-59-g7bca6ae). This is on a 20.04.4 system running snapd version 2.54.3+20.04.1ubuntu0.3 from apt and snapd version 2.56 rev.16010 in snap.

Snap apps that correctly maintain Yaru themeing are Spotify, Thunderbird, Bing-wall, gkt2 snaps like Audacity and Gimp, and QT based Shotwell, Sweethome3d, and Stellarium, Telegram-desktop, Zoomclient, and Boxy-svg never followed themeing so not reporting those.

All snaps are installed from stable channels and are up-to-date