Remove unused _BOOTLOADER defines

keyboards/lets_split/keymaps/zer09/config.h

@@ -35,7 +35,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define MATRIX_ROW_PINS { C6, D7, E6, B4, B5 }
 #define MATRIX_COL_PINS { F7, B1, B3, B2, B6 }
 
-#define CATERINA_BOOTLOADER
 #define USB_MAX_POWER_CONSUMPTION 50
 
 /* Use I2C or Serial, not both */

keyboards/lets_split/rules.mk

@@ -33,10 +33,13 @@ ARCH = AVR8
 #     CPU clock adjust registers or the clock division fuses), this will be equal to F_CPU.
 F_USB = $(F_CPU)
 
-# Bootloader
-#     This definition is optional, and if your keyboard supports multiple bootloaders of
-#     different sizes, comment this out, and the correct address will be loaded
-#     automatically (+60). See bootloader.mk for all options.
+# Bootloader selection
+#   Teensy       halfkay
+#   Pro Micro    caterina
+#   Atmel DFU    atmel-dfu
+#   LUFA DFU     lufa-dfu
+#   QMK DFU      qmk-dfu
+#   atmega32a    bootloadHID
 BOOTLOADER = caterina
 
 # Interrupt driven control endpoint task(+60)