Make default layer size 16-bit (#15286)

Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>

keyboards/jc65/v32u4/keymaps/gam3cat/keymap.c

@@ -224,7 +224,7 @@ void matrix_scan_user(void) {
 }
 
 layer_state_t layer_state_set_user(layer_state_t state) {
-    switch (biton32(state)) {
+    switch (get_highest_layer(state)) {
        case _BL:
            custom_backlight_level(0);
            rgblight_sethsv_noeeprom(180,100,255);