Bug 1478626 - Remove unused Browser:NextTab and Browser:PrevTab commands. r=dao

browser/base/content/browser-sets.inc

@@ -79,8 +79,6 @@
     <command id="Browser:ReloadSkipCache" oncommand="BrowserReloadSkipCache()" disabled="true">
       <observes element="Browser:Reload" attribute="disabled"/>
     </command>
-    <command id="Browser:NextTab" oncommand="gBrowser.tabContainer.advanceSelectedTab(1, true);"/>
-    <command id="Browser:PrevTab" oncommand="gBrowser.tabContainer.advanceSelectedTab(-1, true);"/>
     <command id="Browser:ShowAllTabs" oncommand="gTabsPanel.showAllTabsPanel();"/>
     <command id="cmd_fullZoomReduce"  oncommand="FullZoom.reduce()"/>
     <command id="cmd_fullZoomEnlarge" oncommand="FullZoom.enlarge()"/>