remove carbon offset parameter and batch create_and_buy function

[jchen293]

Description

• Removed withCarbonOffset parameter from create, buy, and regenerateRates functions, this includes the overload functions that used to have the withCarbonOffset parameter
• Removes the undocumented createAndBuy function from the Batch service. The proper usage is to create a batch first and buy it separately

Testing

Removed relevant tests and re-recorded the cassettes.

Pull Request Type

Please select the option(s) that are relevant to this PR.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement (fixing a typo, updating readme, renaming a variable name, etc)