Bump octicons from 19.15.5 to 19.18.0 in /demo (#3681)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.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 (19.15.5)
+    octicons (19.18.0)
     oj (3.16.10)
       bigdecimal (>= 3.0)
       ostruct (>= 0.2)