Update beginners.md (macOS) (#2063)

use macOS instead of MacOS according to 
https://en.wikipedia.org/wiki/macOS

docs/guides/contribute/beginners.md

@@ -36,7 +36,7 @@ To create a local repository, first find and install a Markdown editor that work
 - [MarkText](https://github.com/marktext/marktext) - Free, cross-platform, and open source
 - [Remarkable](https://remarkableapp.github.io/) - Linux and Windows, open source
 - [NvChad](https://nvchad.com/) for the vi/vim user and the nvim client. A lot of plugins are available to enhance the editor for markdown. See [this document](https://docs.rockylinux.org/books/nvchad/) for a nice set of installation instructions.
-- [VS Code](https://code.visualstudio.com/) - Partially open source, by Microsoft. VS Code is a lightweight and powerful editor available for Windows, Linux and MacOS. To contribute to this document project, you should get the following extensions: Git Graph, HTML Preview, HTML Snippets, Markdown All in One, Markdown Preview Enhanced, Markdown Preview Mermaid Support, and any more that catch your fancy.
+- [VS Code](https://code.visualstudio.com/) - Partially open source, by Microsoft. VS Code is a lightweight and powerful editor available for Windows, Linux and macOS. To contribute to this document project, you should get the following extensions: Git Graph, HTML Preview, HTML Snippets, Markdown All in One, Markdown Preview Enhanced, Markdown Preview Mermaid Support, and any more that catch your fancy.
 
 ## Create a local repository