Migrate dynamic_keymap.layer_count < 4 where requried (#22091)

Co-authored-by: Nick Brassel <nick@tzarc.org>

keyboards/bpiphany/pegasushoof/2015/config.h

@@ -20,5 +20,3 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* key matrix size */
 #define MATRIX_ROWS 8
 #define MATRIX_COLS 18
-
-#define DYNAMIC_KEYMAP_LAYER_COUNT 3  // not enough memory for a 4th layer with VIA

keyboards/bpiphany/pegasushoof/2015/info.json

@@ -1,6 +1,9 @@
 {
     "keyboard_name": "Majestouch TKL The Pegasus Hoof 2015",
     "diode_direction": "COL2ROW",
+    "dynamic_keymap": {
+        "layer_count": 3
+    },
     "indicators": {
         "caps_lock": "C6",
         "scroll_lock": "C5",