Bump protobuf from 2.28.0 to 3.7.1

Bumps [protobuf](https://github.com/stepancheg/rust-protobuf) from 2.28.0 to 3.7.1.
- [Changelog](https://github.com/stepancheg/rust-protobuf/blob/master/CHANGELOG-before-3.md)
- [Commits](stepancheg/rust-protobuf@v2.28.0...v3.7.1)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

Cargo.lock

@@ -37,7 +37,7 @@ smallvec = "1.7"
 inferno = { version = "0.11", default-features = false, features = ["nameattr"], optional = true }
 prost = { version = "0.12", optional = true }
 prost-derive = { version = "0.12", optional = true }
-protobuf = { version = "2.0", optional = true }
+protobuf = { version = "3.7", optional = true }
 criterion = {version = "0.5", optional = true}
 aligned-vec = "0.6"