Bump async-trait from 0.1.37 to 0.1.38 (paritytech#306)

Bumps [async-trait](https://github.com/dtolnay/async-trait) from 0.1.37 to 0.1.38.
- [Release notes](https://github.com/dtolnay/async-trait/releases)
- [Commits](dtolnay/async-trait@0.1.37...0.1.38)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Svyatoslav Nikolsky <svyatonik@gmail.com>

bridges/relays/ethereum/Cargo.toml

@@ -9,7 +9,7 @@ license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 ansi_term = "0.12"
 async-std = "1.6.2"
 async-stream = "0.3.0"
-async-trait = "0.1.37"
+async-trait = "0.1.38"
 backoff = "0.2"
 bp-currency-exchange = { path = "../../primitives/currency-exchange" }
 bp-eth-poa = { path = "../../primitives/ethereum-poa" }