[Glitch] Fix spurious error and incorrect state change when adding a reaction twice

Port c06d2ff437 to glitch-soc

Signed-off-by: Thibaut Girka <thib@sitedethib.com>

app/javascript/flavours/glitch/styles/components/announcements.scss

@@ -38,7 +38,6 @@
 
 .announcements {
   background: lighten($ui-base-color, 8%);
-  border-top: 1px solid $ui-base-color;
   font-size: 13px;
   display: flex;
   align-items: flex-end;