Drop the prerelease flag for create-release

Releases in a "pre-release" state are... weird. I'm not going to deal
with their oddities right now, so instead I'm dropping the command
option and hard-coding a `false` at it's usage site.

src/cli.rs

@@ -22,8 +22,6 @@ pub enum Commands {
         draft: bool,
         #[arg()]
         name: String,
-        #[arg(short, long)]
-        prerelease: bool,
         #[arg()]
         tag_name: String,
         #[arg()]