Remove dependency between derive and core crates

Prevents pulling in bevy crates during the build step, which caused issues
with bevy_reflect's documentation feature.

Fixes #9

crates/bevy_eventlistener_derive/Cargo.toml

@@ -12,7 +12,6 @@ categories = ["game-engines", "rendering"]
 proc-macro = true
 
 [dependencies]
-bevy_eventlistener_core = { path = "../bevy_eventlistener_core", version = "0.5.0" }
 quote = "1"
 syn = "2"
 proc-macro2 = "1"