Remove suggestion to use asset key as file name

[soxofaan]

openeo-api/openapi.yaml

Lines 4596 to 4600 in 7483918

	assets:
	description: |-
	Dictionary of asset objects for data that can be downloaded,
	each with a unique key.
	The keys MAY be used by clients as file names.

The keys MAY be used by clients as file names

I'd propose to remove this suggestion.
It's a weak ("may") suggestion, so in practice, clients can not (and consequently should not) depend on the backend providing keys that are safe to use as file name.

refs:

• from allow custom asset names openeo-geopyspark-driver#291 (comment):

  Adding this sentence above to the spec might not have been the wisest decision

• don't assume asset key can directly be used as download file name openeo-python-client#820

[m-mohr]

Indeed, the sentence doesn't add much, it can be removed.

[soxofaan]

created PR at #583