Update IconButton colors (#30124)

* chore: update `@vector-im/compound-web` to 8.0.0

* refactor(IconButton): use `kind="secondary"` instead of `subtleBackground` props

* test: update snapshots

* fix: force color on room header toggle

* fix: TAC button color

* test(e2e): update release announcement screenshot

res/css/structures/_ThreadsActivityCentre.pcss

@@ -49,12 +49,12 @@
         &:hover,
         &:hover .mx_ThreadsActivityCentreButton_Icon {
             background-color: $quaternary-content;
-            color: $primary-content;
+            fill: $primary-content;
         }
     }
 
     & .mx_ThreadsActivityCentreButton_Icon {
-        color: $secondary-content;
+        fill: $secondary-content;
     }
 }