Switch Quefrency to serial for independent halves (#7262)

keyboards/keebio/quefrency/keymaps/bcat/config.h

@@ -1,6 +1,12 @@
 #pragma once
 
-#define USE_I2C
+/*
+ * Quefrency lacks I2C resistors on the right PCB, so the right half doesn't
+ * work independently. (Presumably the floating I2C lines cause a problem.)
+ * Using serial seems sufficiently fast in practice and allows both halves to
+ * be used independently.
+ */
+#define USE_SERIAL
 
 /* Use an extra LED on the right side since it's wider on the 65% PCB. */
 #undef RGBLED_NUM