Update Rust crate specs to 0.18.0

Author: renovate[bot]

Cargo.toml

@@ -25,7 +25,7 @@ blit = { version = "0.5.12", default-features = false }
 lazy_static = "1.4.0"
 rotsprite = "0.1.3"
 rayon = { version = "1.3.0", optional = true }
-specs = { version = "0.16.1", default-features = false, features = ["specs-derive"] }
+specs = { version = "0.18.0", default-features = false, features = ["specs-derive"] }
 
 [dev-dependencies]
 image = "0.23.3"