Fix error

README.md

@@ -544,7 +544,7 @@ In order to keep from being surprised of breaking changes, it is **highly** reco
 
 ```toml
 [dependencies]
-clap = "~3.0.0"
+clap = "~3.0.0-beta.3"
 ```
 
 This will cause *only* the patch version to be updated upon a `cargo update` call, and therefore cannot break due to new features, or bumped minimum versions of Rust.