INSTALL: remove reference to unimplemented --with-libxml2 option

Author: thegushi

INSTALL

@@ -85,15 +85,12 @@ doesn't find it, you will need to specify the location with
 
 --with-libjansson
 		Location of the jansson JSON library.  Required for reputation
-		query support, unless "--with-libxml2" is also specified.
+		query support.
 
 --with-libmemcached
 		Location of the memcache library.  Enables the "memcache"
 		data set type.
 
---with-libxml2	Location of the XML parser library.  Optional for use
-		with reputation query support.
-
 --with-lua	Lua interpreter library.  Enables fine-grained policy control
 		via Lua script hooks, and also enables building of the
 		"miltertest" test tool.