Make license metadata SPDX compliant (#158)

Author: paolobarbolini

Cargo.toml

@@ -1,9 +1,8 @@
 [package]
-
 name = "httparse"
 version = "1.8.0"
 authors = ["Sean McArthur <[email protected]>"]
-license = "MIT/Apache-2.0"
+license = "MIT OR Apache-2.0"
 description = "A tiny, safe, speedy, zero-copy HTTP/1.x parser."
 repository = "https://github.com/seanmonstar/httparse"
 documentation = "https://docs.rs/httparse"