Addressing SNYK-PYTHON-GUNICORN-6615672, SNYK-PYTHON-CRYPTOGR…

[justinrmiller]

…APHY-6126975

What this PR does / why we need it: Addresses security vulnerabilities in seldon-core.

Which issue(s) this PR fixes: Fixes SNYK-PYTHON-GUNICORN-6615672, SNYK-PYTHON-CRYPTOGRAPHY-6126975 issues.

Special notes for your reviewer: As this is my first PR for seldon-core please help me verify that I haven't introduced any regressions. Thanks!

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