correct agpl license

bindings/rust/Cargo.toml

 [package]
 name = "zenroom"
 version = "0.3.0"
-license = "AGPLv3"
+license = "AGPL-3.0-only"
 description = "Zenroom bindings to execute Zencode inside Rust"
 homepage = "https://zenroom.org"
 repository = "https://github.com/dyne/zenroom"