[Python Lambda SDK] Trim down protobuf when bundling the layer

[selcukcihan]

Description

• Related issue https://linear.app/serverless/issue/SC-606/python-sdk-very-large-extension-layer-size#comment-18e1b26b
• Remove the unused C backend implementation from protobuf when bundling the layer. More information on the backends available in protobuf => https://github.com/protocolbuffers/protobuf/tree/main/python#implementation-backends
• This cuts down the size of the zipped layer archive around 200KB, resulting in a layer of size 650KB when bundled from my local machine

Testing done

Integration tested to make sure removal of the binary does not break the SDK.

[selcukcihan]

@medikoo ready for review 🙏