add variant comment about radiolib

variants/tlora_v2_1_18/platformio.ini

@@ -4,5 +4,8 @@ board = ttgo-lora32-v21
 lib_deps =
   ${esp32_base.lib_deps}
   caveman99/ESP32 Codec2@^1.0.1
+
+; the RADIOLIB_GODMODE flag can be removed once the next version of RadioLib is released. (>5.5.0)
+
 build_flags = 
   ${esp32_base.build_flags} -D TLORA_V2_1_18 -I variants/tlora_v2_1_18 -D RADIOLIB_GODMODE