[1.6.x] Fixed #21625 -- incorrect documentation for DiscoverRunner.build_suite

Backport of b62031441b2e1cb1eeb7e1d6f254c553643add96 from master.
[1.6.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
[1.6.x] Fixed #21613 -- Removed a hardcoded input id from the tutorial.

Thanks Bruno Brouard for the report.

Backport of cc2d960274 from master
[1.6.x] Fixed #21585 -- Updated some links to 3rd party database projects.

Thanks graeme.perrow at sap.com for the original report.

Backport of 23d9f517dc from master