Revert parking lot to 0.11 and bump version

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "futures-intrusive"
 edition = "2018"
-version = "0.4.1"
+version = "0.4.2"
 authors = ["Matthias Einwag <[email protected]>"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/Matthias247/futures-intrusive"
@@ -21,7 +21,7 @@ default = ["std"]
 [dependencies]
 futures-core = { version = "^0.3", default-features = false }
 lock_api = "0.4.1"
-parking_lot = { version = "0.12.0", optional = true }
+parking_lot = { version = "0.11.0", optional = true }
 
 [dev-dependencies]
 futures = { version = "0.3.0", default-features = true, features=["async-await"] }