fix(next): fix type inference for createSingleRouteHandler (#597)

Author: Gabrola

.changeset/gold-moles-sell.md

@@ -0,0 +1,5 @@
+---
+'@ts-rest/next': patch
+---
+
+Fix type inference for `createSingleRouteHandler`

libs/ts-rest/next/src/lib/ts-rest-next.ts

@@ -231,13 +231,9 @@ export const createNextRouter = <T extends AppRouter>(
  * ```typescript
  * export default createNextRouter(contract, implementationHandler);
  * ```
- *
- * @param appRoute
- * @param options
- * @returns
  */
 export function createSingleRouteHandler<T extends AppRoute>(
-  appRoute: AppRoute,
+  appRoute: T,
   implementationHandler: AppRouteImplementation<T>,
   options?: CreateNextRouterOptions,
 ) {