Bump highlight.js from 9.12.0 to 9.18.5 in /client

Bumps [highlight.js](https://github.com/highlightjs/highlight.js) from 9.12.0 to 9.18.5.
- [Release notes](https://github.com/highlightjs/highlight.js/releases)
- [Changelog](https://github.com/highlightjs/highlight.js/blob/9.18.5/CHANGES.md)
- [Commits](https://github.com/highlightjs/highlight.js/compare/9.12.0...9.18.5)

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

client/yarn.lock

@@ -2477,8 +2477,8 @@ he@1.1.x, he@^1.1.0:
   resolved "https://registry.yarnpkg.com/he/-/he-1.1.1.tgz#93410fd21b009735151f8868c2f271f3427e23fd"
 
 highlight.js@^9.6.0:
-  version "9.12.0"
-  resolved "https://registry.yarnpkg.com/highlight.js/-/highlight.js-9.12.0.tgz#e6d9dbe57cbefe60751f02af336195870c90c01e"
+  version "9.18.5"
+  resolved "https://registry.yarnpkg.com/highlight.js/-/highlight.js-9.18.5.tgz#d18a359867f378c138d6819edfc2a8acd5f29825"
 
 history@^3.0.0:
   version "3.3.0"