set dyn_notch_min_hz minimum to 70hz

dyn_notch_min_hz provides a lower frequency limit below which the dynamic notch cannot go.
The current minimum is 100hz.
For low rpm quads (>7" to X class), when the dynamic notch mode is 'LOW', we should allow the user to enter the lowest possible value that can be detected by the FFT.
That is theoretically the centre of the second bin.  In low mode that is half-way between 31 and 63hz.  In practice, that value will be biased upwards a little bit by the uppers shoulder.  In practice the lowest value returned by the FFT is likely to not be less than 60hz.
This PR lowers the limit from 100hz to 60hz, allowing access to the full range of possible FFT tracking frequencies in LOW mode for low rpm quads.

src/main/cli/settings.c

@@ -605,7 +605,7 @@ const clivalue_t valueTable[] = {
     { "dyn_notch_range",           VAR_UINT8   | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_DYNAMIC_FILTER_RANGE }, PG_GYRO_CONFIG, offsetof(gyroConfig_t, dyn_notch_range) },
     { "dyn_notch_width_percent",   VAR_UINT8   | MASTER_VALUE, .config.minmaxUnsigned = { 0, 20 }, PG_GYRO_CONFIG, offsetof(gyroConfig_t, dyn_notch_width_percent) },
     { "dyn_notch_q",               VAR_UINT16  | MASTER_VALUE, .config.minmaxUnsigned = { 1, 1000 }, PG_GYRO_CONFIG, offsetof(gyroConfig_t, dyn_notch_q) },
-    { "dyn_notch_min_hz",          VAR_UINT16  | MASTER_VALUE, .config.minmaxUnsigned = { 100, 1000 }, PG_GYRO_CONFIG, offsetof(gyroConfig_t, dyn_notch_min_hz) },
+    { "dyn_notch_min_hz",          VAR_UINT16  | MASTER_VALUE, .config.minmaxUnsigned = { 60, 1000 }, PG_GYRO_CONFIG, offsetof(gyroConfig_t, dyn_notch_min_hz) },
 #endif
 #ifdef USE_DYN_LPF
     { "dyn_lpf_gyro_min_hz",        VAR_UINT16 | MASTER_VALUE, .config.minmaxUnsigned = { 0, 1000 }, PG_GYRO_CONFIG, offsetof(gyroConfig_t, dyn_lpf_gyro_min_hz) },