[1.5.x] Fixed #21632 -- Docs: Removed example with callable as query parameter

Using callables as query parameters is undocumented and not working,
so this changes an example from the ForeignKey.limit_choices_to
documentation that uses it.

Backport of d34c8c338a from master
[1.5.x] Fixed #21613 -- Removed a hardcoded input id from the tutorial.

Thanks Bruno Brouard for the report.

Backport of cc2d960274 from master