Switch Grayscale Patch for DISCiPLE 3c-3d

While developing the Miles Gordon Technology DISCiPLE interface, the ROM kept being rewritten. While rewriting from v3b to v3c, the SCREEN$ printing routine was set to pixel instead of grayscale printing.#This patch resets the faulty rewrite back to usable grayscale printing of big SCREEN$ in DISCiPLE v3c and v3d.