Issue Description

The docs contain a typo in split_keyboard.md under the section describing SPLIT_USB_DETECT (line 447).

"theres's" should be "there's."

• https://docs.qmk.fm/features/split_keyboard

• qmk_firmware/docs/features/split_keyboard.md

  Line 447 in f0a5db9

  Enabling this option changes the startup behavior to listen for an active USB communication to delegate which part is master and which is slave. With this option enabled and theres's USB communication, then that half assumes it is the master, otherwise it assumes it is the slave.