remove broken polargraph link

README.md

@@ -36,7 +36,6 @@ A curated list of code and resources for computer-controlled drawing machines an
 - [EggBot](https://egg-bot.com) - Pen plotter for egg-shaped and spherical objects.
 - [HP Pen Plotters](https://www.hpmuseum.net/exhibit.php?class=4&cat=24) - Vintage desktop and floor-standing pen plotters from the creator of the HPGL standard. Model 7475A is very common and can usually be found on eBay.
 - [Roland Pen Plotters](https://www.youtube.com/watch?v=6_pwzqPk6Gg) - Vintage flatbed HPGL pen plotters. Search eBay for "roland dxy".
-- [Polargraph](http://www.polargraph.co.uk) - The original polargraph hardware and software project.
 - [BrachioGraph](https://brachiograph.readthedocs.io/en/latest/) - A cheap and simple plotter made from sticks, servos, and a Raspberry Pi running Python.
 - [Arduino CNC Drawing Machine](https://www.diymachines.co.uk/arduino-cnc-drawing-machine) - A fairly simple 3d-printed AxiDraw-style plotter with good video documentation.