Update CONTRIBUTING.rst

Co-authored-by: Brigitta Sipőcz <[email protected]>

Author: keflavich

CONTRIBUTING.rst

@@ -66,7 +66,7 @@ New contributions are generally not allowed to bring along additional dependenci
 
 The astropy ecosystem tools should be used whenever possible.
 For example, `astropy.table` should be used for table handling,
-`astropy.io.ascii` for ascii-table parsing, and `astropy.units` for unit and quantity
+or `astropy.units` for unit and quantity
 handling.