Revert pinned version for protobuf

[adba-msft]

Description

Reverts PR #3452 which caused a version conflict.

ERROR: Cannot install -r sdk/python/dev-requirements.txt (line 9) and protobuf==3.20.1 because these package versions have conflicting dependencies.

The conflict is caused by:
    The user requested protobuf==3.20.1
    tensorflow 2.9.3 depends on protobuf<3.20 and >=3.9.2

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