Typo fix, buils -> builds

Pointed out by Alexander Law.

doc/src/sgml/install-windows.sgml

@@ -84,7 +84,7 @@
 
  <para>
   Both 32-bit and 64-bit builds are possible with the Microsoft Compiler suite.
-  32-bit PostgreSQL buils are possible with
+  32-bit PostgreSQL builds are possible with
   <productname>Visual Studio 2005</productname> to
   <productname>Visual Studio 2015</productname> (including Express editions),
   as well as standalone Windows SDK releases 6.0 to 7.1.