CachedFeatureFlagStore breaks if you supply size argument

[adambom]

Problem: if you instantiate a CachedFeatureFlagStore by supplying a size argument, subsequent calls to set will fail with a TypeError.

Repro steps:

from flipper import MemoryFeatureFlagStore, CachedFeatureFlagStore

s = CachedFeatureFlagStore(MemoryFeatureFlagStore(), size=10)

s.set('a', True)

> TypeError: set() got an unexpected keyword argument 'size'