Bug 1371744 Put a margin around the legacy page heading r=mstriemer

MozReview-Commit-ID: KVDcCytDR6Y

--HG--
extra : rebase_source : 24abf2552b373d8e92c0aa2f534a68f22dc0c654

toolkit/themes/shared/extensions/extensions.inc.css

@@ -1090,7 +1090,8 @@ button.button-link:not([disabled="true"]):active:hover {
   background-color: #fcf8ed;
 }
 
-#disabled-unsigned-addons-info {
+#disabled-unsigned-addons-info,
+#legacy-extensions-info {
   margin-bottom: 2em;
   margin-right: 48px;
   margin-left: 48px;