Refrain from overwriting the span status for unfinished spans

[marandaneto]

Description

Context getsentry/team-mobile#128

[marandaneto]

sentry-dart/dart/lib/src/sentry_tracer.dart

Lines 88 to 95 in 0aaa46e

	// finish unfinished spans otherwise transaction gets dropped
	final spansToBeFinished = _children.where((span) => !span.finished);
	for (final span in spansToBeFinished) {
	await span.finish(
	status: SpanStatus.deadlineExceeded(),
	endTimestamp: commonEndTimestamp,
	);
	}

solution can be reverted since Relay does it internally now.
Check PR and see if there are more changes that need to be reverted.
Make sure that transactions get ingested after the changes and default values are applied by Relay correctly.
This should be based on v8 branch and add a note about older versions of Sentry self hosted.