image reading from s3 is broken with dask_image.imread in current pip / conda build

**What happened**:
Directly reading images from URLs is deprecated since 3.4 and will no longer be supported two minor releases later. Please open the URL for reading and pass the result to Pillow, e.g. with ``PIL.Image.open(urllib.request.urlopen(url))``.

**What you expected to happen**:
Reads correctly from s3 url and maintains backward compatibility

**Minimal Complete Verifiable Example**:

```python
import dask.dataframe as dd
df = dd.read_csv('s3://mybucket/mycsv.csv') #no problem

import dask_image.imread
img = dask_image.imread.imread('s3://mybucket/myimg.png') # yes problem

```

**Anything else we need to know?**:

**Environment**:

dask 2021.5.0 pyhd8ed1ab_0 conda-forge
dask-core 2021.5.0 pyhd8ed1ab_0 conda-forge
dask-image 0.6.0 pyhd8ed1ab_0 conda-forge
pillow 8.2.0 py39h5fdd921_1 conda-forge
pims 0.5 pyh9f0ad1d_1 conda-forge
s3fs 2021.5.0 pyhd8ed1ab_0 conda-forge

- Python version: 3.9.4
- Operating System: OSX Big Sir v 11.3