build(deps): update rocksdb requirement from 0.15 to 0.16 (#537)

Updates the requirements on [rocksdb](https://github.com/rust-rocksdb/rust-rocksdb) to permit the latest version.
- [Release notes](https://github.com/rust-rocksdb/rust-rocksdb/releases)
- [Changelog](https://github.com/rust-rocksdb/rust-rocksdb/blob/master/CHANGELOG.md)
- [Commits](rust-rocksdb/rust-rocksdb@v0.15.0...v0.16.0)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

kvdb-rocksdb/Cargo.toml

@@ -19,7 +19,7 @@ log = "0.4.8"
 num_cpus = "1.10.1"
 parking_lot = "0.11.1"
 regex = "1.3.1"
-rocksdb = { version = "0.15", features = ["snappy"], default-features = false }
+rocksdb = { version = "0.16", features = ["snappy"], default-features = false }
 owning_ref = "0.4.0"
 parity-util-mem = { path = "../parity-util-mem", version = "0.9", default-features = false, features = ["std", "smallvec"] }