[nrf fromlist] samples: boards: nordic: coresight_stm: Fix nrfutil trace command

Latest version of nrfutil trace doesn't support setting
uart baudrate.
Remove --baudrate {baudrate_val} from command that executes nrfutil.

Upstream PR #: 83939

Signed-off-by: Sebastian Głąb <[email protected]>

Author: nordic-segl

samples/boards/nordic/coresight_stm/pytest/test_stm.py

@@ -110,7 +110,6 @@ def _nrfutil_dictionary_from_serial(
     collect_time: float = 60.0,
 ) -> None:
     UART_PATH = dut.device_config.serial
-    UART_BAUDRATE = dut.device_config.baud
     dut.close()
 
     logger.debug(f"Using serial: {UART_PATH}")
@@ -132,7 +131,7 @@ def _nrfutil_dictionary_from_serial(
     cmd = (
         "nrfutil trace stm --database-config "
         f"{config_str} "
-        f"--input-serialport {UART_PATH} --baudrate {UART_BAUDRATE} "
+        f"--input-serialport {UART_PATH} "
         f"--output-ascii {decoded_file_name}"
     )
     try: