Change column-dropdown icon

[shpaass]

The following image shows a Modules-column-header:

A user (kaisermaeximus) said that the triangle could be mistaken for a sorting indicator, and one does not mess with sorting for no reason.

In other words, a user misinterpreted the meaning of the triangle as a sorting indicator instead of a dropdown.
This is not their fault because it really looks like one of the sorting indicators.

Therefore the issue can be described as follows:

Problem:
The indicator for a dropdown menu of the columns is confusing.

Solution:
Change the dropdown icon to something less confusing. A mini-hamburger icon, maybe?

[veger]

Now I cannot unsee... How did we never noticed ourselves?!