Sometimes time moves slowly and strict comparison is not enough:
```
> assert now < node_cache_item.last_used < time.time()
E assert 1614147958.869299 < 1614147958.869299
E + where 1614147958.869299 = <parso.cache._NodeCacheItem object at 0x10456fe80>.last_used
E + and 1614147958.869299 = <built-in function time>()
E + where <built-in function time> = time.time
test/test_cache.py:149: AssertionError
```
In particular, macOS timings can be a bit coarse.
The test failure is from Apple Silicon M1.
Cache files that weren't accessed in the last 30 days will be automatically
garbage collected. This collection happens when the `save_module` is called
via a lock system that would make it happen only one time per day.
