[R][Docs] pkgdown generation is failing

[kou]

Describe the bug, including details regarding any error messages, version, and platform.

For example: AMD64 Debian 12 Complete Documentation

https://github.com/apache/arrow/actions/runs/15427917957/job/43419320955#step:7:11460

-- Building pkgdown site for package arrow -------------------------------------
Reading from: /build/r
Writing to: /build/r/docs
-- Sitrep ----------------------------------------------------------------------
v URLs ok.
v Favicons ok.
v Open graph metadata ok.
v Articles metadata ok.
x Reference metadata not ok.
  In _pkgdown.yml, 1 topic missing from index: "one".
  Either add to the reference index, or use `@keywords internal` to drop from
  the index.

Component(s)

Documentation, R

[kou]

@jonkeane @thisisnic @amoeba We may need to update _pkgdown.yml.

[kou]

Issue resolved by pull request 46722
#46722