Bug 1465973 - Stop setting font-size: 13px on panel headers. r=jaws

MozReview-Commit-ID: EXK2OGeEyZr

--HG--
extra : rebase_source : d7ad83ea40a71f53649db0e11b614f0421cc0aa8

browser/themes/shared/customizableui/panelUI.inc.css

@@ -1592,7 +1592,6 @@ toolbarpaletteitem[place="menu-panel"] > .subviewbutton-nav::after {
 
 .panel-header > label {
   flex: auto;
-  font-size: 13px;
   font-weight: 600;
   margin: 0;
   text-align: center;