Duplicate resources assignment to pins PC6 and PC7 in GEPR-GEPRCF722_BT_HD

[dargoo]

See: https://github.com/betaflight/config/blob/fb1b58d41a6efb2c86637acad5126fc367312a88/configs/GEPRCF722_BT_HD/config.h#L41-L61

#define MOTOR2_PIN           PC6
...
#define MOTOR4_PIN           PC7
...
#define UART6_TX_PIN         PC6
...
#define UART6_RX_PIN         PC7

I cannot find RX6 and TX6 pads in the current GEPRC SPAN F722-BT-HD V2 Stack User Manual.

In GEPRC MARK5 DC HD O3 (with GPS mounted and configured by GEPRC ) I had Betaflight 4.3.2 and "diff" output with:

resource SERIAL_TX 6 NONE
resource SERIAL_RX 6 NONE

[dargoo]

I wanted to suggest changes, but @haslinghuis you're really quick. Thank you