fix: remove redundant None from dict.get() calls

[Ratish1]

Description

Removes explicit 'None' default values from '.get()' calls in 'agent.py' and 'sagemaker.py'.

The 'dict.get()' method defaults to 'None' already, so this change makes explicitly passing None as the second argument
unnecessary.

Related Issues

N/A

Documentation PR

N/A

Type of Change

Refactor

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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