build(deps): bump plek from 5.3.0 to 5.3.1

Bumps [plek](https://github.com/alphagov/plek) from 5.3.0 to 5.3.1.
- [Changelog](https://github.com/alphagov/plek/blob/main/CHANGELOG.md)
- [Commits](alphagov/plek@v5.3.0...v5.3.1)

---
updated-dependencies:
- dependency-name: plek
  dependency-version: 5.3.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -564,7 +564,7 @@ GEM
     pg (1.6.3-aarch64-linux)
     pg (1.6.3-arm64-darwin)
     pg (1.6.3-x86_64-linux)
-    plek (5.3.0)
+    plek (5.3.1)
     pp (0.6.3)
       prettyprint
     prettyprint (0.2.0)