Fix BranchProtection.restrictions raising AttributeError

[Noethix55555]

Fixes #3526.

Problem

BranchProtection.restrictions raises AttributeError: 'dict' object has no attribute 'value' whenever push restrictions are present. The property returns self._restrictions.value, but _useAttributes stored the raw API dict instead of wrapping it like every other attribute. The absent-restrictions case only worked because NotSet.value is None.

Solution

Wrap the value with _makeDictAttribute, consistent with how all other attributes are handled:

self._restrictions = self._makeDictAttribute(attributes["restrictions"])

The _user_push_restrictions / _team_push_restrictions lines are left unchanged since they read raw URL strings and already work.

Tests

Added two regression tests in tests/BranchProtection.py that construct a BranchProtection offline (mock requester, no network):

• testRestrictionsPopulated builds a populated top-level restrictions object and asserts bp.restrictions["users"] / ["teams"] round-trip.
• testRestrictionsAbsent asserts an absent restrictions still yields None.

The populated test fails on main with the reported AttributeError and passes with the fix.