Allow for sleep to be called more times than expected

[musicinmybrain]

While reviewing a python-rate-limiter package for Fedora Linux, I found that sleep may be called more times than expected in the tests. On Fedora Linux Rawhide on x86_64 with Python 3.11, it is called 3 times instead of 2.

Loosen the assertion so that this doesn’t fail test_sleep.

[vutran1710]

seem this test is kinda flaky, isnt it? I need to think about the root cause first. I think patching like this is not gonna help in the long run

[vutran1710]

@musicinmybrain Please see #99