[Keyboard] Fix Compile issues for Signum 3.0 (#14588)

* [Keyboard] Fix Compile issues for Signum 3.0

* quantuuum

keyboards/signum/3_0/signum.c → keyboards/signum/3_0/3_0.c

@@ -13,4 +13,4 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-#include "signum.h"
+#include "3_0.h"

keyboards/signum/3_0/elitec/elitec.h

@@ -1,4 +1,3 @@
 #pragma once
 
-#include "quantum.h"
-#include "signum.h"
+#include "3_0.h"

keyboards/signum/3_0/teensy/teensy.h

@@ -15,5 +15,4 @@
  */
 #pragma once
 
-#include "quantum.h"
-#include "signum.h"
+#include "3_0.h"