Bug 1536514 - actually close quote of 'PanelUI-fxa' for fxa menu keypress handler, r=vbudhram

Differential Revision: https://phabricator.services.mozilla.com/D24067

--HG--
extra : moz-landing-system : lando

browser/base/content/browser.xul

@@ -1089,7 +1089,7 @@
 
         <toolbarbutton id="fxa-toolbar-menu-button" class="toolbarbutton-1 badged-button"
                        onmousedown="gSync.toggleAccountPanel('PanelUI-fxa', event)"
-                       onkeypress="gSync.toggleAccountPanel('PanelUI-fxa, event)"
+                       onkeypress="gSync.toggleAccountPanel('PanelUI-fxa', event)"
                        consumeanchor="fxa-toolbar-menu-button"
                        closemenu="none"
                        label="&fxa.menu.firefoxAccount;"