[libadwaita] (17 commits) ...stylesheet: Stop special casing popovers in dark variant

[Alexander Mikhaylenko <alexm src gnome org>]

Summary of changes:

  2f03e25... stylesheet: Clean up assistant sidebar (*)
  25ac0df... stylesheet: Remove .sidebar border (*)
  d72a94f... demo: Stop overriding sidebar styles (*)
  4384b9a... demo: Add .background to the flap sidebar (*)
  cd8a13b... demo: Fix a typo (*)
  ad60bd8... stylesheet: Remove sidebar background (*)
  26f97ee... stylesheet: Don't explicitly set menu colors (*)
  8bbcd8a... stylesheet: Extract popover colors (*)
  7cb8699... stylesheet: Extract backdrop headerbar color (*)
  aeb8c4b... stylesheet: Reorganize tab border color (*)
  e152872... stylesheet: Move notebook tab color to header instead (*)
  f081d24... stylesheet: Refresh tab bar styles (*)
  28337e2... stylesheet: Use $dark_fg and $light_fg less (*)
  7dc4836... stylesheet: Extract card colors (*)
  10b6cda... stylesheet: Unify header bar and dark fill colors (*)
  774a6ff... stylesheet: Refresh background colors (*)
  7622a78... stylesheet: Stop special casing popovers in dark variant (*)

(*) This commit already existed in another branch; no separate mail sent