docs(lambda-nodejs): fix default runtime docs (#27984)

With #26763 the default runtime was reverted from NODEJS_18_X to NODEJS_16_X
This PR reflects this in the docs of the NodejsFunctionProps


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packages/aws-cdk-lib/aws-lambda-nodejs/lib/function.ts

@@ -38,7 +38,7 @@ export interface NodejsFunctionProps extends lambda.FunctionOptions {
    * The runtime environment. Only runtimes of the Node.js family are
    * supported.
    *
-   * @default Runtime.NODEJS_18_X
+   * @default `Runtime.NODEJS_LATEST` if the `@aws-cdk/aws-lambda-nodejs:useLatestRuntimeVersion` feature flag is enabled, otherwise `Runtime.NODEJS_16_X`
    */
   readonly runtime?: lambda.Runtime;