docs(plugins): point Career Coach marketing docs link at its Quick start (protoLabsAI#1768)

careercoach-plugin now has a dedicated `## Quick start` how-to; repoint the
marketing catalog `links.docs` from #readme to #quick-start so the /plugins
page's docs link lands on the guide (matches the plugin manifest's guide_url).

Co-authored-by: Josh Mabry <artificialcitizens@gmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

sites/marketing/data/plugins.json

@@ -179,7 +179,7 @@
     "install": "https://github.com/protoLabsAI/careercoach-plugin",
     "links": {
       "source": "https://github.com/protoLabsAI/careercoach-plugin",
-      "docs": "https://github.com/protoLabsAI/careercoach-plugin#readme"
+      "docs": "https://github.com/protoLabsAI/careercoach-plugin#quick-start"
     }
   }
 ]