Update packages/angular_devkit/build_angular/src/builders/dev-server/builder.ts

This is not necessary

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: tianma630

packages/angular_devkit/build_angular/src/builders/dev-server/builder.ts

@@ -98,7 +98,7 @@ export function execute(
                 hmr: boolean;
                 allowedHosts: true | string[];
                 define: { [key: string]: string } | undefined;
-                middlewareConfig: string;
+                middlewareConfig?: string;
               },
               builderName,
               (options, context, codePlugins) => {