Verify Python==3.13 when running make build

[asjohnston-asf]

Per the README, when manually building/deploying HyP3, the user needs to make sure they're running Python v3.13 when pip installing the lambda dependencies:

• Install Python dependencies for AWS Lambda functions (requires pip for python 3.13)

make build

Missing this step and building with a different version of python can lead to import or runtime errors when the lambda functions run with an AWS Python 3.13 runtime after being deployed.

It should be simple to assert python --version starts with 3.13 within the make build target itself, to prevent this error up front in the future.

https://github.com/ASFHyP3/hyp3/blob/develop/Makefile#L17