fix: error message for MinItems validator (#389)

Signed-off-by: Mostafa Hussein <mostafa.hussein91@gmail.com>

validate.go

@@ -87,7 +87,7 @@ func MinItems(numberItems int) Validator {
 			// if the list is shorter than the given value
 			if len(list) < numberItems {
 				// yell loudly
-				return fmt.Errorf("value is too long. Min items is %v", numberItems)
+				return fmt.Errorf("value is too short. Min items is %v", numberItems)
 			}
 		} else {
 			// otherwise we cannot convert the value into a list of answer and cannot enforce length