JetBrains: Make icons consistent in Sourcegraph menu

Created by: vdavid

Context

We have this in the context menu:

And this on the action palette:

Problem

1. It looks weird that some context menu items have an icon while others don't.
2. The icon on the sub-items actually adds more clutter than value.

Solution

Probably the best solution would be to have the icon only for the main context menu item, and no icon for the sub-items. But the actions on the action palette are loaded from the same source as for the context menu, and we want the icons in the action palette. So not sure if we can remove the icons from the context menu sub-items but not from the action palette items.

If we can't do that, then just add the missing icon to the sub-item, which solves problem no. 1.