Remove link to pyosmium master doc

Author: joto

pyosmium/index.html

@@ -32,7 +32,6 @@ <h2>Documentation</h2>
 
 <ul id="source-code-reference">
     <li><a target="_blank" href="https://docs.osmcode.org/pyosmium/latest/">latest</a> (latest released version)</li>
-    <li><a target="_blank" href="https://docs.osmcode.org/pyosmium/master/">master</a> (development version)</li>
 </ul>