Remove faulty `throw` statements

The `throw` statements that were recently inserted into these tests have
an observable impact on the parsing behavior: they causes the `"use
strict"` token sequence to be interpreted as a string literal instead of
a directive prolog, which in turn effects how the tests are interpreted.

Remove the new `throw` statements from these tests and rely on
previously-existing statements that serve the same purpose without
impacting program strictness.