Brush cursor is being drawn even if the selected tool is non-brush in
GPv3 paint mode. To prevent this, use `ED_gpencil_brush_cursor_poll` for
`pc` poll function. Above poll function returns false if active tool is not
brush, this will avoid drawing of paint cursor in
`pc->draw`/`grease_pencil_brush_cursor_draw`.
Resolves#122541
Pull Request: https://projects.blender.org/blender/blender/pulls/122657
4b6479bf9e