BranchProtection.restrictions raises AttributeError when push restrictions are present #3526

Describe the bug

Accessing BranchProtection.restrictions raises AttributeError: 'dict' object has no attribute 'value' whenever a branch has push restrictions configured.

The restrictions property returns self._restrictions.value, but _useAttributes stores the raw API dict in self._restrictions rather than wrapping it like every other attribute:

if "restrictions" in attributes:  # pragma no branch
    self._restrictions = attributes["restrictions"]   # raw dict, not wrapped

The absent-restrictions case happens to work only because NotSet.value is None, which is why existing tests (asserting restrictions is None) did not catch this.

Traceback

  File ".../github/BranchProtection.py", line 157, in restrictions
    return self._restrictions.value
           ^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'dict' object has no attribute 'value'

Expected behavior

branch_protection.restrictions returns the restrictions dict (users, teams, apps, etc.) when push restrictions are present.