docs: Document global_lsp_settings.button and remove duplicate docs for lsp_highlight_debounce (#36547)

Follow up to this discussion:
https://github.com/zed-industries/zed/pull/36337

Release Notes:

- N/A

This will (gracefully) break links to
https://zed.dev/docs/configuring-zed#lsp-highlight-debounce-1 I don't
see anything show up for that on google or github search and I don't
think its load bearing.

---------

Co-authored-by: zumbalogy <3770982+zumbalogy@users.noreply.github.com>

docs/src/visual-customization.md

@@ -321,6 +321,12 @@ TBD: Centered layout related settings
     // Defaults to true.
     "cursor_position_button": true,
   },
+  "global_lsp_settings": {
+    // Show/hide the LSP button in the status bar.
+    // Activity from the LSP is still shown.
+    // Button is not shown if "enable_language_server" if false.
+    "button": true
+  },
 ```
 
 ### Multibuffer