rust-cpython: removed now useless py_set() conversion
In rust-cpython 0.3.0, HashSets implement the appropriate
ToPythonObject, we can therefore get rid of this hacky conversion.
There still remains an inefficiency in `MissingAncestors.bases()`:
we have to clone, because `to_py_object()` requires full ownership.
However:
- the only use case outside of unit tests used to be from
`setdiscovery.partialdiscovery` which is now fully implemented
in Rust.
- it's not worse than what `py_set()` used to do
Differential Revision: https://phab.mercurial-scm.org/D7120
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}