Remove backlight_init_ports from duck/orion/v3

[zvecr]

Description

Broken with #7273, empty function without the correct custom driver stuff now produces:

Linking: .build/duck_orion_v3_default.elf                                                           [ERRORS]
 | 
 | .build/obj_duck_orion_v3_default/quantum/backlight/backlight_avr.o: In function `backlight_init_ports':
 | /home/zvecr/Desktop/qmk_firmware/quantum/backlight/backlight_avr.c:449: multiple definition of `backlight_init_ports'
 | .build/obj_duck_orion_v3_default/matrix.o:matrix.c:(.text.backlight_init_ports+0x0): first defined here
 | collect2: error: ld returned 1 exit status

Types of Changes

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

Checklist

• My code follows the code style of this project.
• 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).