CN: Remove noisy and inaccurate u64 index warning for extra (revert #616)

[dc-mak]

#616 intended to warn users when an extract was used with non u64 types for iterated owneds that are create from array types, but it ended up warning for every iterated owned, which is noisy and inaccurate.

After #311 and #499 are implemented (ideally in a way that doesn't block #303), this should be removed because incorrect base types can be warned per extract/focus rather than globally, which would close #256 too (and maybe #357 and #320).