Bump bootstrap from 5.1.3 to 5.2.3

Bumps [bootstrap](https://github.com/twbs/bootstrap-rubygem) from 5.1.3 to 5.2.3.
- [Release notes](https://github.com/twbs/bootstrap-rubygem/releases)
- [Changelog](https://github.com/twbs/bootstrap-rubygem/blob/main/CHANGELOG.md)
- [Commits](https://github.com/twbs/bootstrap-rubygem/compare/v5.1.3...v5.2.3)

---
updated-dependencies:
- dependency-name: bootstrap
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Gemfile

@@ -39,7 +39,7 @@ gem 'sdoc', '~> 2.6.1',          group: :doc
 gem 'web-console', '~> 4.2.0', group: :development
 gem 'listen', '~> 3.7.0', group: :development
 
-gem 'bootstrap', '~> 5.1.3'
+gem 'bootstrap', '~> 5.2.3'
 gem "bootstrap_form", "~> 5.1"
 gem 'font-awesome-sass', '~> 6.4.0'