Tidy up use of CTPC (#19570)

keyboards/ckeys/handwire_101/readme.md

@@ -14,7 +14,7 @@ The laser cutting file is ideal for Ponoko's P1 board size.
 
 If you want to reflash the pre-installed firmware, use the `.bin` file for Proton C and the `.hex` file for Pro Micro builds. Flash with the QMK Toolbox or via the command line.
 
-Building for Proton C: `make ckeys/handwire_101:default CTPC=yes`
+Building for Proton C: `make ckeys/handwire_101:default CONVERT_TO=proton_c`
 Building for Pro Micro: `make ckeys/handwire_101:default`
 
 Pre-built firmware files (and laser cutting case files) can be found here: https://github.com/c-keys/handwire

keyboards/keebio/bdn9/keymaps/codecoffeecode/rules.mk

@@ -1,4 +1,4 @@
 MOUSEKEY_ENABLE = yes
 ifneq (, $(findstring rev1, $(KEYBOARD)))
-  CTPC = yes
+  CONVERT_TO=proton_c
 endif

keyboards/kingly_keys/little_foot/keymaps/yanfali/rules.mk

@@ -1,4 +1,4 @@
-CTPC=yes
+CONVERT_TO=proton_c
 CONSOLE_ENABLE = yes    # Console for debug
 COMMAND_ENABLE = yes     # Commands for debug and configuration
 AUDIO_ENABLE = yes

keyboards/montsinger/rebound/rev1/keymaps/curry/rules.mk

@@ -1 +1 @@
-CTPC = yes
+CONVERT_TO=proton_c

keyboards/shapeshifter4060/keymaps/debug/readme.md

@@ -12,7 +12,7 @@ To compile and flash to the board:
     
 If you want to use this with a Proton C, do this instead:
 
-    make shapeshifter4060:debug CTPC=yes
+    make shapeshifter4060:debug CONVERT_TO=proton_c
 
 To just compile:
 

keyboards/shapeshifter4060/readme.md

@@ -13,7 +13,7 @@ Make example for this keyboard (after setting up your build environment):
     
 For use with the Proton C
     
-    make shapeshifter4060:default CTPC=yes
+    make shapeshifter4060:default CONVERT_TO=proton_c
     
 Flashing example for this keyboard: