Issue follow up: function on top

[leobalter]

For this + other tests that do f(), I think we need to make sure f is a function — otherwise Web-compatible engines produce a ReferenceError which is not what the test is about.

Adding a line above that function f() {} might be sufficient. WDYT?

Originally posted by @mathiasbynens in https://github.com/tc39/test262/pull/3161#discussion_r692777838

[leobalter]

@mathiasbynens @rwaldron I created this to avoid losing track again as the referred PR is closed.

[mathiasbynens]

Thank you!