Remove picoprobe debugger

[lurch]

The picoprobe.cfg file referred to at https://github.com/raspberrypi/pico-project-generator/blob/master/pico_project.py#L93 no longer exists in the openocd repo, and I believe therefore this "PicoProbe" debugger option needs to be removed from pico-project-generator.

@P33M will understand all this better than me, but AFAIK the picoprobe software (which has now been renamed to debugprobe ) used to use a custom debugger-interface (which is what picoprobe.cfg connected to). However with the latest firmware, a Pico-flashed-with-debugprobe_on_pico.uf2 or a DebugProbe-flashed-with-debugprobe.uf2 both now offer the standard CMSIS-DAP debugger-interface, and thus both should use cmsis-dap.cfg (i.e. the ""CMSIS-DAP Debug Probe" option already offered by pico-project-generator).