Fix URL to GitHub issues (#520)

Co-authored-by: Michael Dunphy <[email protected]>

Author: mdunphy

numcodecs/__init__.py

@@ -13,7 +13,7 @@
 
 If you have a question, find a bug, would like to make a suggestion or
 contribute code, please `raise an issue on GitHub
-<https://github.com/alimanfoo/numcodecs/issues>`_.
+<https://github.com/zarr-developers/numcodecs/issues>`_.
 
 """
 import multiprocessing