Use SPDX license format

Author: atouchet

Cargo.toml

@@ -3,7 +3,7 @@ name = "lazy_static"
 # NB: When modifying, also modify html_root_url in lib.rs
 version = "1.4.0"
 authors = ["Marvin Löbel <loebel.marvin@gmail.com>"]
-license = "MIT/Apache-2.0"
+license = "MIT OR Apache-2.0"
 
 description = "A macro for declaring lazily evaluated statics in Rust."
 readme = "README.md"