Added docs, and removed some old, not needed docs

docs/split_keyboards.md

@@ -8,12 +8,6 @@ keyboard.split_flip = True  # If your boards are identical but one is flipped, t
 keyboard.split_offsets = [6, 6, 6, 6]  # This is the how many keys are on each column on the "Master" half
 ```
 
-## Master Half
-Choosing the master half can be done one of 2 ways. You can set this true or false if you only pleg in on one side.
-```python
-keyboard.split_master_left = True
-```
-
 ## EE HANDS
 If you want to plug in on either side, it can be done fairly easily but requires setup. 
 
@@ -34,5 +28,5 @@ from kmk_side import split_side
 To enable uart it's as simple as adding this line, of course changing the pin
 ```python
 keyboard.split_type = "UART"
-keyboard.uart = keyboard.init_uart(tx=board.SCL)
+keyboard.uart_pin = board.SCL
 ```