[Core] Remove matrix_is_modified() and debounce_is_active() (#15349)

keyboards/converter/sun_usb/matrix.c

@@ -38,8 +38,6 @@ static uint8_t matrix[MATRIX_ROWS];
 #define ROW(code)      ((code>>3)&0xF)
 #define COL(code)      (code&0x07)
 
-static bool is_modified = false;
-
 __attribute__ ((weak))
 void matrix_init_kb(void) {
     matrix_init_user();
@@ -154,11 +152,6 @@ uint8_t matrix_scan(void)
     return code;
 }
 
-bool matrix_is_modified(void)
-{
-    return is_modified;
-}
-
 inline
 bool matrix_has_ghost(void)
 {