wiki: Wrong indentation of header (trivial change)

[Ashark]

The Configuration.md in the project wiki has wrong indentation:

#### up
This is a gesture that defines the action that will be taken when the scroll wheel is moved up (down if inverted). Refer to the Actions/Gestures section for further info. To function, this field requires target to be enabled.

#### down  # <- Here I added additional hash symbol
This is a gesture that defines the action that will be taken when the scroll wheel is moved down (up if inverted). Refer to the Actions/Gestures section for further info. To function, this field requires target to be enabled.

### thumbwheel
This is an optional object field that defines the thumb wheel settings on a device that supports it (e.g. MX Master 3).