Fix casing of "macOS" (#17040)

This PR fixes a number of spots in English contexts (docs, comments,
etc.) where we were using "MacOS" instead of "macOS".

Release Notes:

- N/A

docs/src/languages/bash.md

@@ -11,7 +11,7 @@ Report issues to: [https://github.com/d1y/bash.zed/issues](https://github.com/d1
 The bash-language-server support shellcheck. But you need to install it manually:
 
 ```sh
-# MacOS
+# macOS
 brew install shellcheck
 
 # Ubuntu/Debian

docs/src/languages/json.md

@@ -8,7 +8,7 @@ JSON support is available natively in Zed.
 ## JSONC
 
 Zed also supports a super-set of JSON called JSONC, which allows single line comments (`//`) in JSON files.
-While editing these files you can use `cmd-/` (MacOS) or `ctrl-/` (Linux) to toggle comments on the current line or selection.
+While editing these files you can use `cmd-/` (macOS) or `ctrl-/` (Linux) to toggle comments on the current line or selection.
 
 <!--
 TBD: JSONC Example for how to use `file_types`

docs/src/languages/luau.md

@@ -19,7 +19,7 @@ To support automatically formatting your code, you can use [JohnnyMorganz/StyLua
 Install with:
 
 ```sh
-# MacOS via HomeBrew
+# macOS via HomeBrew
 brew install stylua
 # Or via Cargo
 cargo install stylua --features lua52,lua53,lua54,luau