hal-qspi_test: remove STM workaround

after feature-qspi branch rebase, everything works fine and workaround is not needed anymore

TESTS/mbed_hal/qspi/flash_configs/STM/DISCO_L475VG_IOT01A/flash_config.h

@@ -18,9 +18,5 @@
 
 #include "../../MX25R6435F_config.h"
 
-// TODO: remove when fixed
-// when perform 4IO write, when memory indicates write finish (changing WIP bit in status register)
-// but actually write is still in progress and we have to wait a bit more before reading
-#define STM_WRITE_4IO_BUG_WORKAROUND
 
 #endif // MBED_QSPI_FLASH_CONFIG_H

TESTS/mbed_hal/qspi/main.cpp

@@ -142,11 +142,6 @@ static void _qspi_write_read_test(Qspi &qspi, qspi_bus_width_t write_inst_width,
 
             timer.stop();
             write_time = timer.read_us();
-#ifdef STM_WRITE_4IO_BUG_WORKAROUND
-            if (write_cmd == QSPI_CMD_WRITE_4IO) {
-                wait_us(2000);
-            }
-#endif
         }
 
         if (read_frequency != QSPI_NONE) {