Fix RF power-creep on TTGOv2 TX

[wvarty]

When using a TTGOv2 dev board as a TX, the RF power slowly increases of it's own accord, as if dynamic power is turned on, even though it is not.
This is a result of a define in the target file for the button pin, which is typically connected to the 5way selector on a module that has a screen.
The unused button pin was floating, and thus triggering random false "presses", which I assume is changing settings and cause power to increase.
Removing the define in the TX target for TTGO has fixed the problem in my testing.

[pkendall64]

The default button action is long-press = increase power. So if there is no button then it could easily do as you say. The pin is defined as INPUT_PULLUP, but sadly this particular pin does not have an internal pullup!