Fix AMBER link (#424)

* Fixes #423
* fix link

Author: lilyminium

doc/source/formats/reference/top.rst

@@ -55,4 +55,4 @@ The format is defined in `PARM parameter/topology file
 specification`_.  The reader tries to detect if it is a newer
 (AMBER 12?) file format by looking for the flag "ATOMIC_NUMBER".
 
-.. _`PARM parameter/topology file specification`: http://ambermd.org/formats.html#topology
+.. _`PARM parameter/topology file specification`: https://ambermd.org/FileFormats.php#topology