Replace Iterable with Generator. (#3726)

* Replace Iterable with Generator for correct types.

config/rollup/rollup.config.js

@@ -180,7 +180,7 @@ function configure(pkg, env, target) {
           file: `packages/${pkg.name}/${pkg.module}`,
           format: 'es',
           sourcemap: true,
-        }
+        },
       ],
       // We need to explicitly state which modules are external, meaning that
       // they are present at runtime. In the case of non-UMD configs, this means