Update link to reference Microsoft's official documentation

Author: erst-neaste

README.md

@@ -77,7 +77,6 @@ with open(target_path, mode="w", encoding="utf-8") as html_file:
 
 # RTF Specification Links
 
-If you find a working official Microsoft link to the RTF specification and add it here, you'll be remembered fondly.
-
-* [Webarchive Link to RTF Spec 1.9.1](https://web.archive.org/web/20190708132914/http://www.kleinlercher.at/tools/Windows_Protocols/Word2007RTFSpec9.pdf)
+* [RTF Informative References](https://learn.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxrtfcp/85c0b884-a960-4d1a-874e-53eeee527ca6)
+* [RTF Spec 1.9.1](https://msopenspecs.azureedge.net/files/Archive_References/[MSFT-RTF].pdf)
 * [RTF Extensions, MS-OXRTFEX](https://docs.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxrtfex/411d0d58-49f7-496c-b8c3-5859b045f6cf)