Fix shared type in _interpreters

[sobolevn]

It is a dict[str, Any] or None:

>>> import _interpreters
>>> i = _interpreters.create()

>>> _interpreters.exec(i, 'print(1)', shared=False)
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    _interpreters.exec(i, 'print(1)', shared=False)
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: _interpreters.exec() argument 3 must be dict, not bool

Non-str keys:

>>> _interpreters.exec(i, 'print(1)', shared={1: 1})
Traceback (most recent call last):
  File "<python-input-4>", line 1, in <module>
    _interpreters.exec(i, 'print(1)', shared={1: 1})
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: bad argument type for built-in operation

Real sharing:

>>> _interpreters.exec(i, 'print(1)', shared={'a': 1})
1

Some objects can't be shared. Currently only a few can be. But, I think that restricting this type yet is not a good idea, because more can be added in the future. Also, (1, 2) is ok, (1, object()) is not

[brianschubert]

(I suppose the last example should be _interpreters.exec(i, 'print(a)', shared={'a': 1}) ;)

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉