fix(curriculum): update test to assert valid year value lab leap year calculator (#65853)

Co-authored-by: majestic-owl448 <26656284+majestic-owl448@users.noreply.github.com>

curriculum/challenges/english/blocks/lab-leap-year-calculator/66c06fad3475cd92421b9ac2.md

@@ -44,6 +44,9 @@ You should declare a variable `year` and assign it a value to check if it is a l
 
 ```js
 assert.isDefined(year);
+assert.isNumber(year);
+assert.isAtLeast(year, 0);
+assert.isTrue(Number.isInteger(year));
 ```
 
 The `year` variable shouldn't be empty.