ref: Simplify Scope.root_span logic

[szokeasaurusrex]

Depends on:

• ref(scope): Properly type Scope.root_span #4273
• feat(scope): Replace transaction with root_span #4263

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
20459	1	20458	4415

View the top 1 failed test(s) by shortest run time

tests.test_basics test_classmethod_tracing

Stack Traces | 0.13s run time

tests/test_basics.py:811: in test_classmethod_tracing
    assert fake_start_child.call_count == 1
E   AssertionError: assert 3 == 1
E    +  where 3 = <MagicMock name='mock.start_child' id='139892869571984'>.call_count

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