docs: update homepage tagline (#704)

## 📝 Description
Update homepage tagline from "The open source delivery platform" to
"All-in-one delivery platform for teams who’ve outgrown default tools"
to match marketing site.

## ✅ Checklist
- [X] I have tested this change
- [ ] This change requires documentation update

Author: TomFern

docs/docusaurus.config.js

@@ -13,7 +13,7 @@ const config = {
   // https://docusaurus.io/docs/next/api/docusaurus-config#noIndex
   noIndex: false,
   title: 'Semaphore',
-  tagline: 'The open source delivery platform',
+  tagline: 'All-in-one delivery platform for teams who’ve outgrown default tools',
   favicon: 'img/favicon.ico',
 
   // extra themes