InputText: Fixed a one-frame display glitch where pressing Escape to revert after a deletion would lead to small garbage being displayed for one frame. (#3008)

Curiously very old, amend 83efdce and bdbb2b2. Using stb_ functions updated ->CurLenA without updating ->TextA, leading to `buf_display_end = buf_display + state->CurLenA;` in the display.
Since f3ab5e62 they are 1 case out of 4 which didn't apply back to ->TextA and this is essentially the one where we ensure appliance. Another solution would be to alter the lower display code, but applying to TextA makes things more consistent.
3 files changed