Bump nokogiri from 1.19.3 to 1.19.4 in /demo (#4103)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

demo/Gemfile.lock

@@ -248,9 +248,9 @@ GEM
     mutex_m (0.3.0)
     netrc (0.11.0)
     nio4r (2.7.5)
-    nokogiri (1.19.3-arm64-darwin)
+    nokogiri (1.19.4-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.19.3-x86_64-linux-gnu)
+    nokogiri (1.19.4-x86_64-linux-gnu)
       racc (~> 1.4)
     octicons (19.28.0)
     oj (3.16.10)