Another typo fix

keyboards/deltasplit75/keymaps/itsaferbie/config.h

@@ -26,6 +26,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifdef SUBPROJECT_v2
     #include "../../v2/config.h"
 #endif
-#ifdef SUBPROJECT_ProtoSplit
+#ifdef SUBPROJECT_protosplit
     #include "../../protosplit/config.h"
 #endif