fix: python3.8 not found during deploy

[luislhl]

Acceptance Criteria

• The deploy pipeline should run successfully

Explanation

We started to have problems with serverless-python-requirements plugin when deploying the Lambdas: https://github.com/HathorNetwork/hathor-explorer-service/actions/runs/3542218948/jobs/5947524789

The error was python3.8 not found.

Setting the python to be used by the plugin to any python3 available solves the issue (reference: https://stackoverflow.com/questions/57740310/serverless-python3-7-not-found-try-the-pythonbin-option)

The new run is working again: https://github.com/HathorNetwork/hathor-explorer-service/actions/runs/3542880636/jobs/5948842767

Security Checklist

• [ ] Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.