Replace links pointing to the Safe Dev Docs

[germartinez]

In the README file of this project some links pointing to the Safe docs need to be updated:

• In line 23
  Replace https://docs.gnosis-safe.io/backend/service-architecture with https://docs.safe.global/safe-core-api/service-architecture

• In line 181
  Replace https://docs.safe.global/learn/infrastructure/rpc-requirements with https://docs.safe.global/safe-core-api/rpc-requirements

• In line 190
  Replace https://docs.safe.global/learn/safe-core/safe-core-api/available-services with https://docs.safe.global/safe-core-api/available-services

I didn't create a Pull Request because I don't have permissions.

[Uxio0]

I was not aware of that, you have now permissions 😉