Fix high ouput timing to 417/833 ns widths

This has the side effect of lengthening the low time proportionally,
to a total of 417 ns longer than necessary.  This does not appear to
have any observable negative impact.

main/main.cpp

@@ -106,7 +106,7 @@ extern "C" void app_main(void) {
     // ScreenLEDs()
     // SPI_LEDs(39);
     LEDStrip *LEDs = new SPI_LEDs(39);
-    int frequency = 60;
+    int frequency = 30;
 
     while (true) {
         // Trash the old preset in case we can't find the set effect

main/spi_leds.cpp

@@ -54,7 +54,9 @@ SPI_LEDs::SPI_LEDs(int _gpio, int length) :
         .cs_ena_posttrans = 0, // moot
         // Datasheet implies 3.2 MHz => 1.25 us / 4
         // We can get away with 4.4_ MHz => 900 ns / 4
-        .clock_speed_hz = 3200000,
+        // HOWEVER, better implementations divide 1.25 us into thirds!
+        // Thus, 2.4 MHz has the same H times and slightly longer L times.
+        .clock_speed_hz = 2400000,
         .input_delay_ns = 0, // moot
         .spics_io_num = -1,
         .flags = 0, // Keep it MSB first