Fix for protobuf deprecation warnings

[scottslewis]

This pull request updates the protoc-generated code in etcd.etcdrpc package by re running the grpc code generator on the etcd3 proto files using

protobuf version: 5.27.2 grpcio and grpcio-tools version: 1.66.1 python version: 3.11

This fixes (through local testing) the warnings generated as described in issue #1823 .

Also updates the version number of python-etcd3 to 0.13.0 in three places.