[receiver-mock] Set opentelemetry-proto version to match the Sumo Logic receiver's version

[aboguszewski-sumo]

To make sure that the tests check actual situations, we should set the proto's version to match the one used by Sumo Logic backend.
Proto will be released as a crate in the next, v0.18 release, according to a comment from an issue from the opentelemetry-rust repository. Earlier releases will probably not be supported, since proto crate didn't exist in v0.17 and earlier.

sumologic-kubernetes-tools/src/rust/receiver-mock/Cargo.toml

Line 26 in c385cda

opentelemetry-proto = { git = "https://github.com/open-telemetry/opentelemetry-rust", features = ["gen-tonic", "build-server", "logs", "metrics"] }