Update parity-scale-codec to prepare for breaking rustc release (#6746)

This updates parity-scale-codec{-derive} to prepare for a rustc release
that would otherwise break the derive implementation:
rust-lang/rust#73084

Author: bkchr

Cargo.toml

@@ -14,7 +14,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 [dependencies]
 linregress = "0.1"
 paste = "0.1"
-codec = { package = "parity-scale-codec", version = "1.3.1", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.3.4", default-features = false }
 sp-api = { version = "2.0.0-rc5", path = "../../primitives/api", default-features = false }
 sp-runtime-interface = { version = "2.0.0-rc5", path = "../../primitives/runtime-interface", default-features = false }
 sp-runtime = { version = "2.0.0-rc5", path = "../../primitives/runtime", default-features = false }