Use SPDX license format

Author: atouchet

Cargo.toml

@@ -1,9 +1,8 @@
 [package]
-
 name = "getopts"
 version = "0.2.21" # don't forget to update html_root_url
 authors = ["The Rust Project Developers"]
-license = "MIT/Apache-2.0"
+license = "MIT OR Apache-2.0"
 readme = "README.md"
 repository = "https://github.com/rust-lang/getopts"
 documentation = "https://doc.rust-lang.org/getopts"