LocalCluster docs give incorrect default value

This isn't a bug, but just notification that there is a typo in the documentation for LocalCluster.

The docstr indicates that the default is 8786, when the actual default is 0.

Someone likely switched the default to 0 while testing and forgot to switch it back. nbd

https://github.com/dask/distributed/blob/074bc4809480a88dfdf4d05e33169fc9c19a69d1/distributed/deploy/local.py#L35

https://github.com/dask/distributed/blob/074bc4809480a88dfdf4d05e33169fc9c19a69d1/distributed/deploy/local.py#L105