Clarify that for repeats, position is always included in XPath path for audit log

https://opendatakit.github.io/xforms-spec/client-audit-logs says "`node`: for events that refer to a specific node, the XPath path of that node". Add something like "In the case of repeats, position predicates are always included even if only one repeat instance currently exists."

Open the client-audit-logs page linked in the issue and find the `node` definition describing XPath paths. Add the clarification that repeat position predicates are always included, even when only one repeat instance exists, then verify the rendered specification contains the new wording.

Written by the indexing model from the issue text.