documentation incorrectly states that `event_cache_size` is unaffected by `caches.global_factor`

[richvdh]

Afaict, this changed in #8563

[richvdh]

(see: https://matrix-org.github.io/synapse/v1.66/usage/configuration/config_documentation.html#event_cache_size)

[richvdh]

related: #13681

[DMRobertson]

Details: the event_cache_size is used here to create an AsyncLRUCache

synapse/synapse/storage/databases/main/events_worker.py

Lines 242 to 247 in 92c5817

	self._get_event_cache: AsyncLruCache[
	Tuple[str], EventCacheEntry
	] = AsyncLruCache(
	cache_name="*getEvent*",
	max_size=hs.config.caches.event_cache_size,
	)

Which passes through to LRUCache:

synapse/synapse/util/caches/lrucache.py

Lines 821 to 830 in 41320a0

	class AsyncLruCache(Generic[KT, VT]):
	"""
	An asynchronous wrapper around a subset of the LruCache API.
	On its own this doesn't change the behaviour but allows subclasses that
	utilize external cache systems that require await behaviour to be created.
	"""
	def __init__(self, *args, **kwargs): # type: ignore
	self._lru_cache: LruCache[KT, VT] = LruCache(*args, **kwargs)

which will scale the max_size by the global factor:

synapse/synapse/util/caches/lrucache.py

Lines 431 to 434 in 41320a0

	if apply_cache_factor_from_config:
	self.max_size = int(max_size * cache_config.properties.default_factor_size)
	else:
	self.max_size = int(max_size)