doc: Fix incorrect version list for Windows SDK

References to SDK 8.1a should have been cleaned up in 495ed0e, as only
version 10 and above are supported with Windows 10 and newer versions.

Reported-by: Thomas Munro
Discussion: https://postgr.es/m/CA+hUKG++qE9uVjQaTTD7oaC8a2T3h8K50=Eqyx9uUZvOHa__ww@mail.gmail.com

Author: michaelpq

doc/src/sgml/install-windows.sgml

@@ -79,9 +79,9 @@
   32-bit PostgreSQL builds are possible with
   <productname>Visual Studio 2015</productname> to
   <productname>Visual Studio 2022</productname>,
-  as well as standalone Windows SDK releases 8.1a to 10.
+  as well as standalone Windows SDK releases 10 and above.
   64-bit PostgreSQL builds are supported with
-  <productname>Microsoft Windows SDK</productname> version 8.1a to 10 or
+  <productname>Microsoft Windows SDK</productname> version 10 and above or
   <productname>Visual Studio 2015</productname> and above.
    <!--
        For 2015 requirements: