Fix duplicate-word typos in docstrings

[Labib-Bin-Salam]

Summary

Two public API docstrings contain accidental repeated words. This fixes both:

• Redditor.multireddits — "For example, to to get ..." → "For example, to get ..." (praw/models/reddit/redditor.py)
• UserSubreddit subscribers attribute — "Count of subscribers. This will be 0 unless unless the authenticated user is a moderator." → "... 0 unless the ..." (praw/models/reddit/user_subreddit.py)

Both strings render in the published API documentation, so the typos are user-visible.

Changes

• Fix the two duplicate-word typos.
• Add myself to the Documentation Contributors list in AUTHORS.rst (per the contributing guide, for a first contribution).

No CHANGES.rst entry, as this is a documentation-only fix with no behavioral change.

Verification

• ruff check passes on both edited files.
• The user_subreddit.py edit keeps the RST simple-table wrapping intact (the description column is 58 chars wide; the edited line is well within it and the following word still wraps to the next line), so docstrfmt reformats nothing.

[Labib-Bin-Salam]

Heads-up on the red CI: the failing docstrfmt lint check is not caused by this change. docstrfmt 2.0.2 crashes during CLI argument parsing under click >= 8.2 (TypeError: main() missing 1 required positional argument: 'section_adornments'), before it reads any file — so it fails on every current PR (the last green main run was 2026-04-27).

The other lint hooks (Static Word Checks, Check Documentation, ruff) all pass here, and running docstrfmt with click pinned < 8.2 formats both edited files cleanly (Done! 🎉), so this change is correctly formatted.

I opened #2102 to pin click < 8.2 on the docstrfmt hook so lint CI goes green again. Once that lands and this branch is rebased, the check here should pass.

[Labib-Bin-Salam]

Updated: I folded the click<8.2 pin for the docstrfmt hook into this PR (the fix originally proposed in #2102), so the lint CI here now passes on its own rather than depending on a separate PR. The change set is now:

• the two docstring typo fixes,
• AUTHORS.rst entry, and
• a one-line additional_dependencies: ["click<8.2"] on the docstrfmt pre-commit hook, with a comment explaining why.

Closing #2102 as superseded by this. Happy to split it back out if you'd prefer the tooling fix as a standalone PR.

[bboe]

I rebased this onto main and dropped the click<8.2 pin commit — an equivalent pin (click<8.4) landed in #2104, so only the typo fixes and AUTHORS.rst entry remain. Thanks for root-causing the docstrfmt/click breakage independently!