Fix: Primer::Beta::RelativeTime does not correctly accept "month" attribute

[HDinger]

What are you trying to accomplish?

The component Primer::Beta::RelativeTime accepts a system_argument[:month]. This was set via fetch_or_fallback method. However, there was the wrong variable used for the first parameter (the allowed values).

Integration

List the issues that this change affects.

Closes #2407

Risk Assessment

• Low risk the change is small, highly observable, and easily rolled back. --> I just used the correct options array instead of the default for the allowed_values
• Medium risk changes that are isolated, reduced in scope or could impact few users. The change will not impact library availability.
• High risk changes are those that could impact customers and SLOs, low or no test coverage, low observability, or slow to rollback.

What approach did you choose and why?

• I decided to also change the defaults for the other options, to their according variables as it looked like copy-past mistake. Since all of them default to nil, it shouldn't make any difference in the result.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Lookbook)
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9c73fdb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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@primer/view-components	Patch

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[keithamus]

Nice catch! LGTM

[lindenthal]

Thanks @HDinger and @keithamus 👍