[Bug][Mobile] section sidebar button overlaps history Clear button

[cclypeatus]

Affects several devices based on testing with Responsive Design Mode.

One quick fix would be to z-index the History box on top of the sidebar button, but it seems to be purposely set to be the other way around right now - History is at z-30, sidebar at z-40. I don't know if there is a good reason for this, but overriding sidebar to be at 29 hasn't introduced any bugs yet at least.