Bump retirement to 0.15.1

[niqjohnson]

We've fixed a couple of bugs in the retrirement app: preventing the retirement translations from leaking into other parts of the site and getting the Spanish mega-menu showing on the Spanish about page. See GHE/CFGOV/platform/issues/3912 for more details.

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Changes

• Bump retirement to 0.15.1
  • Match the cfgov plurals config for translations (Match the cfgov plurals config for translations retirement#263)
  • Show the Spanish mega-menu on about page (Show the Spanish mega-menu on about page retirement#265)

How to test this PR

1. Go to the the retirement tool's Spanish about page, /consumer-tools/retirement/before-you-claim/about/es/. Verify that the Spanish mega-menu is showing on that page.
2. Fill out the Spanish financial wellbeing survey, /consumer-tools/financial-well-being/es/, and get your results. Verify that the "Edad" button is correctly translated on the results page.

Screenshots

Page	0.15.0 (production)	0.15.1 (this PR)
Retirement Spanish about
FWB Spanish results page

Notes and todos

• Some English footer content is still showing up on the Spanish retirement pages, but that seems to be a larger issue that I think we should handle in a separate PR.

Checklist

• PR has an informative and human-readable title
  • PR titles are used to generate the change log in releases; good ones make that easier to scan.
  • Consider prefixing, e.g., "Mega Menu: fix layout bug", or "Docs: Update Docker installation instructions".
• Changes are limited to a single goal (no scope creep)
• Code follows the standards laid out in the CFPB development guidelines
• Future todos are captured in comments and/or tickets