Adjust some paint & brush tools icons

[bsekachev]

My actions before raising this issue

• Read/searched the docs
• Searched past issues

I do not really like two icons I've highlighted, their style looks a bit bolder that for others.
I've taken them from the Internet, maybe it is a good idea to redraw them from scratch.

[rahulsrivastava1]

Hi, I want to work on this issue

[bsekachev]

Hello, @rahulsrivastava1

Actually, this is a ticket for our designer.
That is not about development, I am not sure you should work on it.
If you want to collaborate in the project, you can choose between multiple other issues :)