0xcb/splaytoraid: remove CONVERT_TO at keyboard level

[fauxpark]

Description

Configurator/api_tasks cannot handle converted boards, resulting in the following on the status page:

Ψ Compiling keymap with gmake -r -R -f builddefs/build_keyboard.mk -s KEYBOARD=0xcb/splaytoraid/rp2040_ce KEYMAP=default_configurator KEYBOARD_FILESAFE=0xcb_splaytoraid_rp2040_ce TARGET=0xcb_splaytoraid_rp2040_ce_default_configurator INTERMEDIATE_OUTPUT=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator VERBOSE=false COLOR=true SILENT=false QMK_BIN="qmk" MAIN_KEYMAP_PATH_1=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator MAIN_KEYMAP_PATH_2=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator MAIN_KEYMAP_PATH_3=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator MAIN_KEYMAP_PATH_4=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator MAIN_KEYMAP_PATH_5=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator KEYMAP_JSON=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator/src/keymap.json KEYMAP_PATH=.build/obj_0xcb_splaytoraid_rp2040_ce_default_configurator/src


platforms/chibios/platform.mk:266: lib/chibios/os/hal/lib/streams/streams.mk: No such file or directory
gmake: *** No rule to make target 'lib/chibios/os/hal/lib/streams/streams.mk'.  Stop.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).