[2.0.0] Add missing default TX and RX for T-watch

[happyme531]

That solves

C:\Users\user\.platformio\packages\framework-arduinoespressif32@src-7a495aa357652c59e127d3388578e1f1\cores\esp32\esp32-hal-gpio.c: In function '__pinMode':
C:\Users\user\.platformio\packages\framework-arduinoespressif32@src-7a495aa357652c59e127d3388578e1f1\cores\esp32\esp32-hal-gpio.c:238:44: error: 'RX' undeclared (first use in this function); did you mean 'RX1'?
         pinFunction |= ((uint32_t)(((pin)==RX||(pin)==TX)?0:1) << MCU_SEL_S);
                                            ^~
                                            RX1