Update shared_bindings_synthio_lfo_tick within audiomixer to use variable sample length.

Author: relic-se

shared-module/audiomixer/Mixer.c

@@ -194,7 +194,7 @@ static void mix_down_one_voice(audiomixer_mixer_obj_t *self,
         uint32_t n = MIN(MIN(voice->buffer_length, length), SYNTHIO_MAX_DUR * self->channel_count);
 
         // Get the current level from the BlockInput. These may change at run time so you need to do bounds checking if required.
-        shared_bindings_synthio_lfo_tick(self->sample_rate);
+        shared_bindings_synthio_lfo_tick(self->sample_rate, n / self->channel_count);
         uint16_t level = (uint16_t)(synthio_block_slot_get_limited(&voice->level, MICROPY_FLOAT_CONST(0.0), MICROPY_FLOAT_CONST(1.0)) * (1 << 15));
         #else
         uint32_t n = MIN(voice->buffer_length, length);