Fixed ambiguous term in exercise description

Exercise3.md

@@ -93,13 +93,13 @@ Note: change the output format to support this?
 For example:
 
 ```
-<var-type> <line-number> <column-number> -> obj <line-number> <column-number>
-<var-type> <line-number> <column-number> -> null <line-number> <column-number>
+<update-kind> <line-number> <column-number> -> obj <line-number> <column-number>
+<update-kind> <line-number> <column-number> -> null <line-number> <column-number>
 ```
 
 Here:
 
-- `<var-type>` It represents the type non-null variable.
+- `<update-kind>` It represents the type non-null variable.
   - if the variable is used as an index in array assignment print `NI`.
   - if the variable is an array, print `NA`.
   - Otherwise, print `N`