Auto merge of #4048 - rust-lang:renovate/tower-service-0.x, r=Turbo87

Update Rust crate tower-service to 0.3.1

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [tower-service](https://crates.io/crates/tower-service) | dev-dependencies | patch | `0.3.0` -> `0.3.1` |

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Author: bors

Cargo.toml

@@ -94,7 +94,7 @@ conduit-test = "0.9.0-alpha.5"
 hyper-tls = "0.5"
 lazy_static = "1.4"
 tokio = "1.5.0"
-tower-service = "0.3.0"
+tower-service = "0.3.1"
 
 [build-dependencies]
 diesel = { version = "1.4.8", features = ["postgres"] }