fix: correct groupNumber type in StudentGroupComparator

app/src/test/java/sorting/StudentAvarageGradeComparator.java

@@ -2,10 +2,10 @@ package sorting;
 
 import java.util.Comparator;
 
-public class StudentAverageGradeComparator implements Comparator<Student> {
+public class StudentAvarageGradeComparator implements Comparator<Student> {
 
     @Override
     public int compare(Student s1, Student s2) {
-        return Double.compare(s1.getAverageGrade(), s2.getAverageGrade());
+        return Double.compare(s1.getAvarageGrade(), s2.getAvarageGrade());
     }
 }