crates.io: no_std -> no-std

Apparently this got changed? Or maybe it was never correct.

Cargo.toml

@@ -7,7 +7,7 @@ documentation = "https://docs.rs/byteorder"
 homepage = "https://github.com/BurntSushi/byteorder"
 repository = "https://github.com/BurntSushi/byteorder"
 readme = "README.md"
-categories = ["encoding", "parsing", "no_std"]
+categories = ["encoding", "parsing", "no-std"]
 keywords = ["byte", "endian", "big-endian", "little-endian", "binary"]
 license = "Unlicense OR MIT"
 exclude = ["/ci/*"]