tlora-c6: Disable Screen

MESHTASTIC_EXCLUDE_SCREEN=1 on tlora-c6.

It doesn't have a screen, and this gets it compiling again (saving flash).

Author: vidplace7

variants/esp32c6/tlora_c6/platformio.ini

@@ -8,8 +8,9 @@ build_flags =
   -I variants/esp32c6/tlora_c6
   -DARDUINO_USB_CDC_ON_BOOT=1
   -DARDUINO_USB_MODE=1
-  ; Disable audio.
+  ; Disable screen + audio.
   ; ESP32-C6 with 4MB flash is TIGHT on space.
+  -DMESHTASTIC_EXCLUDE_SCREEN=1
   -DMESHTASTIC_EXCLUDE_AUDIO=1
 
 lib_ignore =