sc-tracing: enable env-filter feature (paritytech#4357)

This crate uses this feature however it appears to still work without
this feature enabled. I believe this is due to feature unification of
the workspace. Some other crate enables this feature so it also ends up
enabled here. But when this crate is pushed to crates.io and compiled
individualy it fails to compile.

substrate/client/tracing/Cargo.toml

@@ -30,7 +30,7 @@ serde = { workspace = true, default-features = true }
 thiserror = { workspace = true }
 tracing = "0.1.29"
 tracing-log = "0.1.3"
-tracing-subscriber = { workspace = true, features = ["parking_lot"] }
+tracing-subscriber = { workspace = true, features = ["env-filter", "parking_lot"] }
 sc-client-api = { path = "../api" }
 sc-tracing-proc-macro = { path = "proc-macro" }
 sp-api = { path = "../../primitives/api" }