build(deps): bump bootstrap from 5.3.5 to 5.3.8 in /site

Bumps [bootstrap](https://github.com/twbs/bootstrap-rubygem) from 5.3.5 to 5.3.8.
- [Release notes](https://github.com/twbs/bootstrap-rubygem/releases)
- [Changelog](https://github.com/twbs/bootstrap-rubygem/blob/main/CHANGELOG.md)
- [Commits](twbs/bootstrap-rubygem@v5.3.5...v5.3.8)

---
updated-dependencies:
- dependency-name: bootstrap
  dependency-version: 5.3.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

site/Gemfile

@@ -19,7 +19,7 @@ end
 
 gem 'json'
 gem "bootswatch", github: "thomaspark/bootswatch", tag: "v5.3.8"
-gem "bootstrap", "~> 5.3.5"
+gem "bootstrap", "~> 5.3.8"
 
 # pinned version of dependency of jekyll-sass-converter, as it emits deprecation warnings until
 # bootstrap v5.5.0 - see https://github.com/OpenTabletDriver/opentabletdriver.github.io/issues/212

site/Gemfile.lock

@@ -12,7 +12,7 @@ GEM
       public_suffix (>= 2.0.2, < 7.0)
     base64 (0.3.0)
     bigdecimal (3.2.2)
-    bootstrap (5.3.5)
+    bootstrap (5.3.8)
       popper_js (>= 2.11.8, < 3)
     colorator (1.1.0)
     concurrent-ruby (1.3.5)
@@ -159,7 +159,7 @@ PLATFORMS
   x86_64-linux-musl
 
 DEPENDENCIES
-  bootstrap (~> 5.3.5)
+  bootstrap (~> 5.3.8)
   bootswatch!
   http_parser.rb (~> 0.6.0)
   jekyll (~> 4.3)