Change default baud rate back to 74906bps, compatible with boot ROM rate

This reverts a behaviour change from 3ceadfc0a6.

examples/experiments/unaligned_load/unaligned_load.c

@@ -3,6 +3,7 @@
 #include "esp/rom.h"
 #include "esp/timer.h"
 #include "espressif/esp_common.h"
+#include "esp/uart.h"
 #include "FreeRTOS.h"
 #include "task.h"
 #include "queue.h"
@@ -213,6 +214,8 @@ void sanity_tests(void);
 
 void user_init(void)
 {
+    uart_set_baud(0, 115200);
+
     gpio_enable(2, GPIO_OUTPUT); /* used for LED debug */
     gpio_write(2, 1); /* active low */