Tiny wording clarification in restic-stats.1.

[will-ca]

What does this PR change? What problem does it solve?

$ man restic-stats is currently more ambiguous than the web docs while describing file-by-contents. It doesn't actually say what happens when a file is "unique".

See:

restic/doc/manual_rest.rst

Lines 300 to 303 in 55d56db

	- ``restore-size`` (default) counts the size of the restored files.
	- ``files-by-contents`` counts the total size of unique files as given by their
	contents. This can be useful since a file is considered unique only if it has
	unique contents. Keep in mind that a small change to a large file (even when the

Was the change previously discussed in an issue or on the forum?

No.

Checklist

• I have read the contribution guidelines.
• I have enabled maintainer edits.
• I have added tests for all code changes.
• I have added documentation for relevant changes (in the manual).
• There's a new file in changelog/unreleased/ that describes the changes for our users (see template).
• I have run gofmt on the code in all commits.
• All commit messages are formatted in the same style as the other commits in the repo.
• I'm done! This pull request is ready for review.

[MichaelEischer]

restic-stats.1 is autogenerated from cmd/restic/cmd_stats.go. Please fix the description there.

[MichaelEischer]

LGTM.