[Requirements] Bound boto3 to <1.17.50 and add botocore explicitly

[Hedingber]

We started seeing packages CI failing with:

Warning!!! Possibly conflicting dependencies found:
* aiobotocore==1.3.0
 - botocore [required: >=1.20.49,<1.20.50, installed: 1.20.50]
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That is happening since botocore recently released 1.20.50, which is incompatible with the latest aiobotocore (which is a sub requirement of s3fs)
boto3 from 1.17.50 requires botocore>=1.20.50,<1.21.0 which conflicts with s3fs 0.5.2 that has aiobotocore>=1.0.1
which resolves to 1.3.0 which has botocore>=1.20.49,<1.20.50, so added <1.17.50 to boto3
boto3 1.17.49 has botocore<1.21.0,>=1.20.49, so we must add botocore explictly