build(deps): update protobuf requirement from ^2.0 to ^3.5

Updates the requirements on [protobuf](https://github.com/stepancheg/rust-protobuf) to permit the latest version.
- [Changelog](https://github.com/stepancheg/rust-protobuf/blob/master/CHANGELOG-before-3.md)
- [Commits](stepancheg/rust-protobuf@v2.0.0...v3.5.0)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -27,7 +27,7 @@ fnv = "^1.0"
 lazy_static = "^1.4"
 libc = { version = "^0.2", optional = true }
 parking_lot = "^0.12"
-protobuf = { version = "^2.0", optional = true }
+protobuf = { version = "^3.5", optional = true }
 memchr = "^2.3"
 reqwest = { version = "^0.12", features = ["blocking"], optional = true }
 thiserror = "^1.0"