Bump rss from 0.3.0 to 0.3.1

Bumps [rss](https://github.com/ruby/rss) from 0.3.0 to 0.3.1.
- [Release notes](https://github.com/ruby/rss/releases)
- [Changelog](https://github.com/ruby/rss/blob/master/NEWS.md)
- [Commits](ruby/rss@0.3.0...0.3.1)

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

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

Gemfile.lock

@@ -9,9 +9,9 @@ GEM
  mini_mime (1.1.5)
  minitest (5.24.1)
  multi_xml (0.6.0)
- rexml (3.3.3)
+ rexml (3.3.4)
  strscan
- rss (0.3.0)
+ rss (0.3.1)
  rexml
  strscan (3.1.0)