Remove transitive dependency version hacks

In the past we required the specification of unused direct dependencies
to make sure that our minimum supported Rust version build works
properly. By now it appears as if warp has fixed their broken version
specifications and if we bump it to 0.3.4, we can drop this hack. So do
just that.

Author: d-e-s-o

Cargo.toml

@@ -43,19 +43,12 @@ structopt = {version = "0.3.20"}
 tokio = {version = "1.34", default-features = false, features = ["rt"]}
 tracing = {version = "0.1", default-features = false, features = ["std"]}
 tracing-subscriber = {version = "0.3", default-features = false, features = ["ansi", "env-filter", "fmt"]}
-warp = {version = "0.3", default-features = false}
+warp = {version = "0.3.4", default-features = false}
 
 [dev-dependencies]
 tempfile = "3.1"
 test-fork = "0.1.3"
 tokio = {version = "1.34", default-features = false, features = ["macros", "rt"]}
 
-# A set of unused dependencies that we require to force correct minimum
-# versions of transitive dependencies, for cases where our dependencies
-# have incorrect dependency specifications themselves.
-_headers_version_unused = {package = "headers", version = "0.3.1"}
-_pkg-config_unused = {package = "pkg-config", version = "0.3.16"}
-_serde_urlencoded_unused = {package = "serde_urlencoded", version = "0.7.1"}
-
 [target.'cfg(not(target_os = "windows"))'.dev-dependencies]
 _openssl_sys_unused = {package = "openssl-sys", version = "0.9.64"}