Re-enable or delete the assertion in fetch_sprout_final_treestates()

[teor2345]

Motivation

The auditors have suggested that this commented-out assertion should either be deleted, or enabled but disabled in tests:

zebra/zebra-state/src/service/check/anchors.rs

Lines 158 to 172 in c838383

	/* TODO:
	- fix tests that generate incorrect root data
	- assert that roots match the fetched tree during tests
	- move this CPU-intensive check to sprout_anchors_refer_to_treestates()
	assert_eq!(
	input_tree.root(),
	joinsplit.anchor,
	"anchor and fetched input tree root did not match:\n\
	anchor: {anchor:?},\n\
	input tree root: {input_tree_root:?},\n\
	input_tree: {input_tree:?}",
	anchor = joinsplit.anchor
	);
	*/

We can do this using #[cfg(not(test))].

Testing

Our existing integration tests should cover this.

[teor2345]

In PR #6450 I resolved this issue by deleting the outdated assertion, and updating the TODO so it only applies to tests.

(We can't do this check in production because it could use a lot of CPU.)