The commit bumps luafun to the new version with a bunch of bugfixes:
* Now `chain` works correctly with iterators without `param`.
* Now `drop_while` supports stateful iterators.
* The module is populated with missing `maximum_by` alias of `max_by`.
* Now `nth` and `length` work correctly with other luafun iterators.

Since our index iterators are stateful (can return different values
with the same `state` passed), the old `drop_while` implementation
didn't work well with them - it was skipping an extra element.
The bump resolves this issue.

Note that there are still methods that don't work correctly with
`index:pairs` - `cycle`, `head` and `is_null`.

Closes tarantool#6403

NO_DOC=bugfix

(cherry picked from commit ec75886)