Comment 5 for bug 1785563

This can't be changed easily and would require a complete rewrite of the grid code.
But you can disable the grid.

Background: The grid is OpenGL texture with a fixed size which is remapped to the corresponding projection. If we reduce the line thickness in the texture the grid will be not visible for a wide fov (e.g. 360 deg HFOV). So the thickness was optimized for wider fov which is more often used then very small fov as your screenshot.