proxy: refactor a collapsible_match (#1214)

src/proxy.rs

@@ -279,11 +279,8 @@ impl Proxy {
             // Custom *may* match 'http', so assume so.
             | Intercept::Custom(_) => true,
             Intercept::System(ref system) => {
-                if let Some(proxy) = system.get("http") {
-                    match proxy {
-                        ProxyScheme::Http { auth, .. } => auth.is_some(),
-                        _ => false,
-                    }
+                if let Some(ProxyScheme::Http { auth, .. }) = system.get("http") {
+                    auth.is_some()
                 } else {
                     false
                 }