Bump docs/themes/uswds from 631e114 to ac7915f

Bumps [docs/themes/uswds](https://github.com/usnistgov/hugo-uswds) from `631e114` to `ac7915f`.
- [Release notes](https://github.com/usnistgov/hugo-uswds/releases)
- [Commits](usnistgov/hugo-uswds@631e114...ac7915f)

---
updated-dependencies:
- dependency-name: docs/themes/uswds
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>