Remove Memos broken demo link, update homepage (#3786)

- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/3558
- https://memos.onrender.com/ : HTTP 404
- https://demo.usememos.com/:  This service has been suspended.

README.md

@@ -1425,7 +1425,7 @@ _Related: [Wikis](#wikis)_
 - [Livebook](https://livebook.dev) - Realtime collaborative notebook app based on Markdown that supports running Elixir codesnippets, TeX and Mermaid Diagrams. Easily deployed using Docker or Elixir. ([Source Code](https://github.com/livebook-dev/livebook)) `Apache-2.0` `Elixir`
 - [Markdown Edit](https://github.com/georgeOsdDev/markdown-edit/) - Online markdown editor/viewer. `MIT` `HTML5`
 - [Meemo](https://meemo.minimal-space.de/) - Personal notes stream with Markdown support. ([Source Code](https://github.com/nebulade/meemo)) `MIT` `Nodejs`
-- [Memos](https://github.com/usememos/memos) - An open source, self-hosted knowledge base that works with a SQLite db file. ([Demo](https://memos.onrender.com/)) `MIT` `Docker/Go`
+- [Memos](https://usememos.com/) - An open source, self-hosted knowledge base that works with a SQLite db file. ([Source Code](https://github.com/usememos/memos)) `MIT` `Docker/Go`
 - [minimalist-web-notepad](https://github.com/pereorga/minimalist-web-notepad) - Minimalist notepad.cc clone. ([Demo](https://notes.orga.cat/)) `Apache-2.0` `PHP`
 - [MiniNote](https://github.com/muety/mininote) - Simple Markdown note-taking app with persistence. `MIT` `Nodejs`
 - [Notes'n'Todos](https://github.com/larspontoppidan/notesntodos) - Write notes and todos online in markdown with tag filtering and date sorting. ([Demo](https://lpss.dk/nnt-playground/)) `MIT` `Python`