Execution of gitpuller in shell throws KeyError: 'branch' version tag 0.10.0

### Bug description
execute gitpuller from bash/shell like this: `gitpuller https://github.com/jupyterhub/nbgitpuller.git` fails.

#### Expected behaviour
Execution shall work with or without specifying a branch value on the command line
see application of that eg. here https://zero-to-jupyterhub.readthedocs.io/en/latest/jupyterhub/customizing/user-environment.html?highlight=gitpuller#using-multiple-profiles-to-let-users-select-their-environment

#### Actual behaviour
`File "/opt/conda/lib/python3.9/site-packages/nbgitpuller/pull.py", line 73, in __init__ self.branch_name = kwargs.pop("branch") KeyError: 'branch'`

### Source of Bug
Since in 0.10.0 the argument "branch" is removed by commit https://github.com/jupyterhub/nbgitpuller/commit/12f25dd45d09d140038a9f9c4b66d7b7cb3ea715#diff-50b85d13b73c3cf1fbf0047f5786d5e8ddba9f959b617c0354d15c399ab47539

https://github.com/jupyterhub/nbgitpuller/blob/3280fdde5d9abc64e4b6271375bd03e94886103d/nbgitpuller/pull.py#L73

### set up
JupyterHub 1.3.0 20210609150206 on microk8s 1.21 with ubuntu 20.04
jupyter base notebook image