fix wrong error message in DateOfVisit

src/main/java/seedu/address/logic/parser/ParserUtil.java

@@ -134,7 +134,7 @@ public static DateOfVisit parseDateOfVisit(String dov) throws ParseException {
         requireNonNull(dov);
         String trimmedDov = dov.trim();
         if (!DateOfVisit.isValidDateOfVisit(trimmedDov)) {
-            throw new ParseException(DateOfBirth.MESSAGE_CONSTRAINTS);
+            throw new ParseException(DateOfVisit.MESSAGE_CONSTRAINTS);
         }
         return new DateOfVisit(trimmedDov);
     }