Make msg request count same colour as per convo unread message count.

Author: ianmacd

ts/components/leftpane/MessageRequestsBanner.tsx

@@ -45,7 +45,8 @@ const StyledCircleIcon = styled.div`
 const StyledUnreadCounter = styled.div`
   font-weight: bold;
   border-radius: var(--margins-sm);
-  background-color: var(--conversation-tab-bubble-background-color);
+  color: var(--unread-messages-alert-text-color);
+  background-color: var(--unread-messages-alert-background-color);
   margin-left: var(--margins-sm);
   min-width: 20px;
   height: 20px;