Fixed test - moved super into top level function

[jonjanisch]

This is a trivial change to fix a test for super.

While reading the tests, I saw the super_in_top_level_function.lox mistakenly had the super at the top level instead of in a top level function.

  super.bar(); // Error at 'super': Can't use 'super' outside of a class.
fun foo() {
}

This change makes the test case for super_in_top_level_function.lox similar to this_in_top_level_function.lox:

fun foo() {
  super.bar(); // Error at 'super': Can't use 'super' outside of a class.
}