CI: fix mypy complaint introduced in #29873
@jreback the pertinent `delete` methods are never hit in tests.  any chance we can rip them out?
> the pertinent delete methods are never hit in tests. any chance we can rip them out?

If `delete` and `remove` are considered private, then the answer should be yes.  `delete` is only ever called by `remove`, and `remove` is only ever called with kwargs such that it never calls `delete`
 the ``.delete`` method you just annotated is likely abstract so yes.

``.remove`` is public and calls the ``.delete`` method on the storer > .remove is public and calls the .delete method on the storer

Darn. If we could remove `where, start, stop` from the signature (in tests these are never passed) we could rule out `delete` ever getting called.

Anyway, this should fix the CI k merge on green. py36 failure is due to a 0.1 microsecond lag between calls, should be ignored > py36 failure is due to a 0.1 microsecond lag between calls, should be ignored

this is the now comparison test? let's just change that test to be better