Use chevron-right for collapsed state

Summary: I find this much more intuitive that it's unexpanded, than a down arrow.

Reviewed By: mweststrate

Differential Revision: D19429007

fbshipit-source-id: 7b414aeee846a864641941b6837770252cb298de

src/chrome/mainsidebar/MainSidebar2.tsx

@@ -119,7 +119,7 @@ const SidebarSection: React.FC<{
           {typeof title === 'function' ? title(collapsed) : title}
           {level < 3 && children && (
             <Glyph
-              name={collapsed ? 'chevron-down' : 'chevron-up'}
+              name={collapsed ? 'chevron-right' : 'chevron-up'}
               size={12}
               color={color}
             />
@@ -520,7 +520,7 @@ const PluginList = memo(function PluginList({
               <Glyph
                 color={colors.macOSTitleBarIconBlur}
                 size={8}
-                name={collapsed ? 'chevron-down' : 'chevron-up'}
+                name={collapsed ? 'chevron-right' : 'chevron-up'}
               />
             </ShowMoreButton>
           )}>