Enter Dashboard URL text field: pressing Enter is different from pressing the search button

**What happened**:

Pressing `Enter` compared to pressing the Search icon when having entered a Dask Dashboard URL provides different outcomes.



I've realized that if I hover the Search icon button, it sais "Auto-detect Dashboard URL" which is what has confused me, pressing enter and doing a "auto-detect dashboard URLs" are different, but based on the layout I assumed they were the same: to submit the suggested URL explicitly written out.

**My wish**

I wish that the UI didn't end up confusing me. I have never been able to have a functional auto-detect button, and that probably makes me even more confused.

**Minimal Complete Verifiable Example**:

I don't know how to provide this =/

**Environment**:

JupyterHub (1.1.1 Helm chart) + Dask-Gateway (0.9.0 Helm chart).

```
$ conda list | grep dask
dask 2021.6.0 pyhd8ed1ab_0 conda-forge
dask-core 2021.6.0 pyhd8ed1ab_0 conda-forge
dask-gateway 0.9.0 py38h578d9bd_0 conda-forge
dask-glm 0.2.0 py_1 conda-forge
dask-kubernetes 2021.3.1 pyhd8ed1ab_0 conda-forge
dask-labextension 5.0.2 pyhd8ed1ab_0 conda-forge
dask-ml 1.9.0 pyhd8ed1ab_0 conda-forge
pangeo-dask 2021.06.05 hd8ed1ab_0 conda-forge
```

```
$ python --version
Python 3.8.10
```

Operating System: Ubuntu 20.04
Install method: conda-forge

```
DASK_DISTRIBUTED__DASHBOARD_LINK=/user/{JUPYTERHUB_USER}/proxy/{port}/status
DASK_GATEWAY__ADDRESS=http://10.100.116.39:8000/services/dask-gateway/
DASK_GATEWAY__AUTH__TYPE=jupyterhub
DASK_GATEWAY__CLUSTER__OPTIONS__IMAGE={JUPYTER_IMAGE_SPEC}
DASK_GATEWAY__PROXY_ADDRESS=gateway://traefik-prod-dask-gateway.prod:80
DASK_GATEWAY__PUBLIC_ADDRESS=/services/dask-gateway/
DASK_LABEXTENSION__FACTORY__CLASS=GatewayCluster
DASK_LABEXTENSION__FACTORY__MODULE=dask_gateway
DASK_ROOT_CONFIG=/srv/conda/etc
```