PR #25543 removed the `_uid` field in favor of the `_id` field,
including for use in slicing.
This removes an outdated reference to `_uid` in our reindex docs.
Previously, a reindex request had two different size specifications in the body:
* Outer level, determining the maximum documents to process
* Inside the source element, determining the scroll/batch size.
The outer level size has now been renamed to max_docs to
avoid confusion and clarify its semantics, with backwards compatibility and
deprecation warnings for using size.
Similarly, the size parameter has been renamed to max_docs for
update/delete-by-query to keep the 3 interfaces consistent.
Finally, all 3 endpoints now support max_docs in both body and URL.
Relates #24344
This further applies the pattern set in #34125 to reduce copy-and-paste
in the multi-document CRUD portion of the High Level REST Client docs.
It also adds line wraps to snippets that are too wide to fit into the box
when rendered in the docs, following up on the work started in #34163.
James Rodewig
Henning Andersen
Mayya Sharipova
Przemyslaw Gomulka
Nik Everett
Sohaib Iftikhar