Bump multipart-post from 2.3.0 to 2.4.0

Bumps [multipart-post](https://github.com/socketry/multipart-post) from 2.3.0 to 2.4.0.
- [Release notes](https://github.com/socketry/multipart-post/releases)
- [Changelog](https://github.com/socketry/multipart-post/blob/main/changelog.md)
- [Commits](socketry/multipart-post@v2.3.0...v2.4.0)

---
updated-dependencies:
- dependency-name: multipart-post
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -119,7 +119,7 @@ GEM
     method_source (1.0.0)
     minitest (5.15.0)
     multi_json (1.15.0)
-    multipart-post (2.3.0)
+    multipart-post (2.4.0)
     nenv (0.3.0)
     nio4r (2.7.0)
     notiffany (0.1.3)