`lpci release` assumes the branch to have an upstream

[Michał Sawicz]

```
2023-11-14 11:16:30.888 Starting lpci, version 0.2.4
2023-11-14 11:16:30.893 lpci internal error: CalledProcessError(1, ['git', 'config', 'branch.launchpad-ppa.remote'])
2023-11-14 11:16:30.894 Traceback (most recent call last):
2023-11-14 11:16:30.894 File "/snap/lpci/158/lib/lpci/main.py", line 130, in main
2023-11-14 11:16:30.894 ret = dispatcher.run() or 0
2023-11-14 11:16:30.894 File "/snap/lpci/158/lib/craft_cli/dispatcher.py", line 448, in run
2023-11-14 11:16:30.894 return self._loaded_command.run(self._parsed_command_args)
2023-11-14 11:16:30.894 File "/snap/lpci/158/lib/lpci/commands/release.py", line 159, in run
2023-11-14 11:16:30.894 self._check_args(args)
2023-11-14 11:16:30.894 File "/snap/lpci/158/lib/lpci/commands/release.py", line 74, in _check_args
2023-11-14 11:16:30.894 current_remote_url = get_current_remote_url()
2023-11-14 11:16:30.894 File "/snap/lpci/158/lib/lpci/git.py", line 40, in get_current_remote_url
2023-11-14 11:16:30.894 current_remote = subprocess.run(
2023-11-14 11:16:30.894 File "/snap/lpci/158/usr/lib/python3.8/subprocess.py", line 516, in run
2023-11-14 11:16:30.894 raise CalledProcessError(retcode, process.args,
2023-11-14 11:16:30.894 subprocess.CalledProcessError: Command '['git', 'config', 'branch.launchpad-ppa.remote']' returned non-zero exit status 1.
2023-11-14 11:16:30.894 Full execution log: '/home/michal/.local/state/lpci/log/lpci-20231114-111630.887610.log'
```