Remove work-in-progress notice in string buffer docs.

doc/ext_buffer.html

@@ -88,12 +88,6 @@ The string buffer library also includes a high-performance
 <a href="serialize">serializer</a> for Lua objects.
 </p>
 
-<h2 id="wip" style="color:#ff0000">Work in Progress</h2>
-<p>
-<b style="color:#ff0000">This library is a work in progress. More
-functionality will be added soon.</b>
-</p>
-
 <h2 id="use">Using the String Buffer Library</h2>
 <p>
 The string buffer library is built into LuaJIT by default, but it's not