Revert "fixed dict in list for Exp _single_params"

This reverts commit 4129693460e7d1fcf20396e4c7c0d439144514a9.
Revert "fixed dict in list for Sersic _single_params"

This reverts commit 22515b8e0bd271edb3c03ead98c9baa4ae4c767d.