Clean a number of sp_io imports (#6072)

Author: kianenigma

Cargo.toml

@@ -12,27 +12,27 @@ repository = "https://github.com/paritytech/substrate/"
 targets = ["x86_64-unknown-linux-gnu"]
 
 [dependencies]
-sp-core = { version = "2.0.0-dev", default-features = false, path = "../../primitives/core" }
 codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
 sp-inherents = { version = "2.0.0-dev", default-features = false, path = "../../primitives/inherents" }
 sp-authorship = { version = "2.0.0-dev", default-features = false, path = "../../primitives/authorship" }
 sp-std = { version = "2.0.0-dev", default-features = false, path = "../../primitives/std" }
 sp-runtime = { version = "2.0.0-dev", default-features = false, path = "../../primitives/runtime" }
 frame-support = { version = "2.0.0-dev", default-features = false, path = "../support" }
 frame-system = { version = "2.0.0-dev", default-features = false, path = "../system" }
-sp-io ={ path = "../../primitives/io", default-features = false , version = "2.0.0-dev"}
 impl-trait-for-tuples = "0.1.3"
 
+[dev-dependencies]
+sp-core = { version = "2.0.0-dev", path = "../../primitives/core" }
+sp-io ={ version = "2.0.0-dev", path = "../../primitives/io" }
+
 [features]
 default = ["std"]
 std = [
 	"codec/std",
-	"sp-core/std",
 	"sp-inherents/std",
 	"sp-runtime/std",
 	"sp-std/std",
 	"frame-support/std",
 	"frame-system/std",
-	"sp-io/std",
 	"sp-authorship/std",
 ]