Use "en" instead of "en-US" in language priority

- Previously, when you accessed the test page with a locale not
  supported Apache returned a forbidden error. This update changes the
  value of LanguagePriority from "en-US" to "en" to correct this issue.
  Now, when you access the test page with a locale not supported, Apache
  returns the test page in English language.

SOURCES/welcome.conf

@@ -22,7 +22,7 @@ Alias /noindex /usr/share/httpd/noindex
   AddLanguage zh-HK .zh-HK
   AddLanguage zh-TW .zh-TW
 
-  LanguagePriority en-US
+  LanguagePriority en
   ForceLanguagePriority Fallback
 
   AllowOverride None