fix(uart): documentation using UART_CLK_SRC_RTC now

Author: SuGlider

cores/esp32/HardwareSerial.h

@@ -375,7 +375,7 @@ class HardwareSerial : public Stream {
   // UART_CLK_SRC_APB          :: ESP32, ESP32-S2, ESP32-C3 and ESP32-S3
   // UART_CLK_SRC_PLL          :: ESP32-C2, ESP32-C5, ESP32-C6, ESP32-C61, ESP32-H2 and ESP32-P4
   // UART_CLK_SRC_XTAL         :: ESP32-C2, ESP32-C3, ESP32-C5, ESP32-C6, ESP32-C61, ESP32-H2, ESP32-S3 and ESP32-P4
-  // UART_CLK_SRC_RTC_FAST     :: ESP32-C2, ESP32-C3, ESP32-C5, ESP32-C6, ESP32-C61, ESP32-H2, ESP32-S3 and ESP32-P4
+  // UART_CLK_SRC_RTC          :: ESP32-C2, ESP32-C3, ESP32-C5, ESP32-C6, ESP32-C61, ESP32-H2, ESP32-S3 and ESP32-P4
   // UART_CLK_SRC_REF_TICK     :: ESP32 and ESP32-S2
   // Note: CLK_SRC_PLL Freq depends on the SoC - ESP32-C2 has 40MHz, ESP32-H2 has 48MHz and ESP32-C5, C6, C61 and P4 has 80MHz
   // Note: ESP32-C6, C61, ESP32-P4 and ESP32-C5 have LP UART that will use only RTC_FAST or XTAL/2 as Clock Source