Multiple Ui improvements (#7029)

* PLT-7119 - Updating headings on compact view

* PLT-7103 - Removing line below channel intro

* PLT-7112 - Fixing system console banner

* PLT-7144 - Adding ellipsis to system console boxes

* PLT-7181 - Changing channel header opacity

* PLT-6899 - Updating unread bar

* Updating margin for new messages indicator

webapp/sass/layout/_headers.scss

@@ -249,8 +249,7 @@
 }
 
 .channel-intro {
-    border-bottom: 1px solid $light-gray;
-    margin: 0 auto 15px;
+    margin: 0 auto 10px;
     padding: 0 15px;
 
     &.channel-intro--centered {