settings: Remove margin for subheader title.

The margin doesn't scale with font size, so it looks
extra weird at small font sizes, and also the text
is already being centered with flex so we don't need
margin.

web/styles/subscriptions.css

@@ -391,7 +391,6 @@ h4.user_group_setting_subsection_title {
             -webkit-line-clamp: 2;
             -webkit-box-orient: vertical;
             overflow: hidden;
-            margin: 20px 10px 0;
 
             &.showing-info-title {
                 display: -webkit-box;