chore: make pin-project-lite dep optional (#51)

Author: MegaRedHand

concurrency/Cargo.toml

@@ -10,7 +10,7 @@ spawned-rt = { workspace = true }
 tracing = { workspace = true }
 futures = "0.3.1"
 thiserror = "2.0.12"
-pin-project-lite = "0.2"
+pin-project-lite = { version = "0.2", optional = true }
 
 [dev-dependencies]
 # This tokio imports are only used in tests, we should not use them in the library code.
@@ -22,4 +22,4 @@ path = "./src/lib.rs"
 
 [features]
 # Enable this to log warnings when non-blocking GenServers block the runtime for too much time
-warn-on-block = []
+warn-on-block = ["dep:pin-project-lite"]