m: Remove unused portable-atomic feature

I added half of a portable-atomic implementation in #86 and forgot to finish it.
This removes it prior to release.

Signed-off-by: John Nunley <dev@notgull.net>

Cargo.toml

@@ -18,20 +18,12 @@ exclude = ["/.*"]
 event-listener = { version = "5.0.0", default-features = false }
 event-listener-strategy = { version = "0.5.0", default-features = false }
 pin-project-lite = "0.2.11"
-portable-atomic-util = { version = "0.1.4", default-features = false, optional = true, features = ["alloc"] }
-
-[dependencies.portable_atomic_crate]
-package = "portable-atomic"
-version = "1.2.0"
-default-features = false
-optional = true
 
 [target.'cfg(loom)'.dependencies]
 loom = { version = "0.7", optional = true }
 
 [features]
 default = ["std"]
-portable-atomic = ["portable-atomic-util", "portable_atomic_crate"]
 std = ["event-listener/std", "event-listener-strategy/std"]
 loom = ["event-listener/loom", "dep:loom"]