feat(uart): update Kconfig.projbuild to reflect functionality

Author: SuGlider

Kconfig.projbuild

@@ -125,9 +125,10 @@ config ARDUINO_SERIAL_FORCE_IDF_DEFAULT_CLOCK_SOURCE
         Overrides Arduino's automatic UART clock selection with the default clock from IDF (clk_tree_defs.h).
         By default, Arduino optimizes the UART clock automatically: XTAL clock for C2, S3, C3, C6, H2, P4 and 
         REF_TICK (<250k baud) or APB (>250k baud) for ESP32, S2.
+        It also overrrides HardwareSerial::setClockSource(), by always forcing the default uart clock source as defined in IDF. 
         Enable this option only if you need to force IDF's default clock instead of Arduino's optimized settings.
         It is generally recommended to leave this disabled unless specifically required.
-        Note: This configuration is not applicable to the low-power (LP) UART controller.
+        Note: This configuration is also applicable to the low-power (LP) UART controller, whenever this is available.
 
 choice ARDUINO_UDP_RUNNING_CORE
     bool "Core on which Arduino's UDP is running"