Remove unused tokio in rust hyper client (#13835)

This crate version has an indirect security vuln,
as tokio-core 0.1.18 (latest) is two years old,
and uses tokio 0.1.5.
https://rustsec.org/advisories/RUSTSEC-2021-0124

modules/openapi-generator/src/main/resources/rust/Cargo.mustache

@@ -35,8 +35,3 @@ version = "^0.11"
 features = ["json", "multipart"]
 {{/supportAsync}}
 {{/reqwest}}
-
-[dev-dependencies]
-{{#hyper}}
-tokio-core = "*"
-{{/hyper}}

samples/client/petstore/rust/hyper/petstore/Cargo.toml

@@ -16,6 +16,3 @@ hyper-tls = "~0.5"
 http = "~0.2"
 base64 = "~0.7.0"
 futures = "^0.3"
-
-[dev-dependencies]
-tokio-core = "*"

samples/client/petstore/rust/reqwest/petstore-async/Cargo.toml

@@ -14,5 +14,3 @@ uuid = { version = "^1.0", features = ["serde"] }
 [dependencies.reqwest]
 version = "^0.11"
 features = ["json", "multipart"]
-
-[dev-dependencies]

samples/client/petstore/rust/reqwest/petstore-awsv4signature/Cargo.toml

@@ -15,5 +15,3 @@ aws-sigv4 = "0.3.0"
 http = "0.2.5"
 secrecy = "0.8.0"
 reqwest = "~0.9"
-
-[dev-dependencies]

samples/client/petstore/rust/reqwest/petstore/Cargo.toml

@@ -12,5 +12,3 @@ serde_json = "^1.0"
 url = "^2.2"
 uuid = { version = "^1.0", features = ["serde"] }
 reqwest = "~0.9"
-
-[dev-dependencies]