Bump octicons from 19.18.0 to 19.19.0 in /demo

Bumps [octicons](https://github.com/primer/octicons_gem) from 19.18.0 to 19.19.0.
- [Commits](https://github.com/primer/octicons_gem/commits)

---
updated-dependencies:
- dependency-name: octicons
  dependency-version: 19.19.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

demo/Gemfile.lock

@@ -241,7 +241,7 @@ GEM
     nio4r (2.7.4)
     nokogiri (1.18.10-x86_64-linux-gnu)
       racc (~> 1.4)
-    octicons (19.18.0)
+    octicons (19.19.0)
     oj (3.16.10)
       bigdecimal (>= 3.0)
       ostruct (>= 0.2)