Tweak the backlight PWM rate to be higher that audio range. Fixes #1571

Author: tannewt

shared-module/displayio/Display.c

@@ -121,7 +121,7 @@ void common_hal_displayio_display_construct(displayio_display_obj_t* self,
     // Always set the backlight type in case we're reusing memory.
     self->backlight_inout.base.type = &mp_type_NoneType;
     if (backlight_pin != NULL && common_hal_mcu_pin_is_free(backlight_pin)) {
-        pwmout_result_t result = common_hal_pulseio_pwmout_construct(&self->backlight_pwm, backlight_pin, 0, 5000, false);
+        pwmout_result_t result = common_hal_pulseio_pwmout_construct(&self->backlight_pwm, backlight_pin, 0, 50000, false);
         if (result != PWMOUT_OK) {
             self->backlight_inout.base.type = &digitalio_digitalinout_type;
             common_hal_digitalio_digitalinout_construct(&self->backlight_inout, backlight_pin);