'assetManager' => [
            'bundles' => [
                'yiiwebPjaxAsset' => [
                    'js'=>[]
                ],
            ],
        ],

'assetManager' => [
    'bundles' => [
        'yiiwebPjaxAsset' => [
            'sourcePath' => null,
            'js'=> ['//cdn.url.you/want/to/use']
        ],
    ],
],

'assetManager' => [
    'bundles' => [
        'yiiwebPjaxAsset' => false,
   ],
]

'assetManager' => [
    'bundles' => false,
]