NOTES-WINDOWS: fix typo

CLA: trivial

(cherry picked from commit fb97b8e8a52b853b2b2209d5aeee36eaa08bb9ad)

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/14042)

NOTES-WINDOWS.md

@@ -89,8 +89,8 @@ variables.
 
 For VC-WIN32, the following defaults are use:
 
-    PREFIX:      %ProgramFiles(86)%\OpenSSL
-    OPENSSLDIR:  %CommonProgramFiles(86)%\SSL
+    PREFIX:      %ProgramFiles(x86)%\OpenSSL
+    OPENSSLDIR:  %CommonProgramFiles(x86)%\SSL
 
 For VC-WIN64, the following defaults are use: