Remove Zeyla Hellyer as an author of Serenity

Requested by them as they're no longer involved with the library's development.

Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-authors = ["alex <acdenissk69@gmail.com>", "Zeyla Hellyer <hi@zeyla.me>"]
+authors = ["Alex M. M. <acdenissk69@gmail.com>"]
 description = "A Rust library for the Discord API."
 documentation = "https://docs.rs/serenity"
 homepage = "https://github.com/serenity-rs/serenity"