Revise documentation for social feed JavaScript model (#10817)

* Revise documentation for social feed JavaScript model

Updated the document to include a note about the deprecation of the SharePoint social feed JavaScript object model and added links to alternative APIs.

* Mark SharePoint mobile authentication content as legacy

Update the overview of the SharePoint mobile client authentication object model to indicate that the content is legacy and provide guidance for current development practices.

* fixing warning

* Revise documentation for Excel Services UDFs

Updated the content and formatting of the Excel Services UDFs documentation, including improvements in clarity and structure.

* docs: date fixup and address findings from Acrolinx report and content formatting cleanup

- revert `ms.date` to original publication date; rendering engine
  shows last modified date dynamically from git history
- collapse runs of blank lines and remove blank lines between
  adjacent list items
- normalize ordered list markers to `1.` and unordered to `- `
  with single space between marker and content
- remove legacy `<a name="...">` anchors; rely on heading slugs
- left-align fenced code blocks, normalize language tags, and
  convert 4-space indentation to 2-space in code samples
- strip leading/trailing blank lines inside code fences
- collapse double spaces in prose (frontmatter and code blocks
  untouched)

* docs: fix broken intra-file anchor links and convert Note callout

- replace removed `#bkmk_*` and `#bk_CreateApp` anchor links with
  heading-slug references for intra-file navigation
- convert plain `> Note:` paragraph to `> [!NOTE]` admonition block
- reindent nested sublist under list item to 4-space indent

* docs: fix inline code formatting inside link text

- move backticks inside link brackets so `[name](url)` becomes
  [`name`](url) and renders the link text as inline code

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Co-authored-by: Andrew Connell <me@andrewconnell.com>

Author: Ashlesha-MSFT