aioboto3: wrong get_credentials type

[dacevedo12]

Describe the bug
aioboto3 Session.get_credentials actually returns a coroutine

>>> import aioboto3
>>> aioboto3.Session()
Session(region_name='us-east-1')
>>> aioboto3.Session().get_credentials()
<coroutine object AioSession.get_credentials at ...>
>>>

but types-aioboto3 even latest types it as a def instead of async def

[vemel]

Hello.

Thanks for your report. The issue only exists in dynamic version of aioboto3 stubs. The fix will be included in the next release.