docs: Rephrase incorrect step in expiration policy docs.

What does this MR do?

This MR repThe previous wording seems to be incorrect/reversed. If you exclude any tags older than X from the list of objects to delete, the objects older then X will not be deleted, while the objects newer than X will be deleted. An alternate change would be to write something like "exclude items newer than ...", but that didn't sound too good considering that the setting name is older_than.

Author's checklist (required)

• Follow the Documentation Guidelines and Style Guide.

• Apply the documentation label, (i don't seem to be able to do this)

  • The corresponding DevOps stage and group label, if applicable.

• Assign the designated Technical Writer.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Optional: Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.
  • Add Technical Writing and docs:: workflow label.
  • Add docs-only when the only files changed are under doc/*.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set.
3. If there has not been a technical writer review, create an issue for one using the Doc Review template.