update serde_qs so the error enum is compatible with Anyhow, fix deprecated warning

Cargo.toml

@@ -20,7 +20,7 @@ reqwest = { version = "0.10.8", default-features = false, features = ["json", "b
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 serde_urlencoded = "0.6.1"
-serde_qs = "0.6.0"
+serde_qs = "0.8.4"
 url = "2.1.1"
 tap-reader = "1"
 toml = { version = "0.5.0", optional = true }

src/registration.rs

@@ -297,7 +297,7 @@ impl Registered {
             .append_pair("response_type", "code")
             .append_pair("force_login", &self.force_login.to_string());
 
-        Ok(url.into_string())
+        Ok(url.into())
     }
 
     /// Create an access token from the client id, client secret, and code