handle more network errors

```python-traceback
Traceback (most recent call last):
  File ".local/bin/github-backup", line 6, in <module>
    sys.exit(main())
             ~~~~^^
  File ".local/share/pipx/venvs/github-backup/lib/python3.14/site-packages/github_backup/cli.py", line 83, in main
    backup_repositories(args, output_directory, repositories)
    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".local/share/pipx/venvs/github-backup/lib/python3.14/site-packages/github_backup/github_backup.py", line 1845, in backup_repositories
    backup_pulls(args, repo_cwd, repository, repos_template)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".local/share/pipx/venvs/github-backup/lib/python3.14/site-packages/github_backup/github_backup.py", line 2019, in backup_pulls
    pulls[number]["commit_data"] = retrieve_data(args, template)
                                   ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File ".local/share/pipx/venvs/github-backup/lib/python3.14/site-packages/github_backup/github_backup.py", line 766, in retrieve_data
    return list(fetch_all())
  File ".local/share/pipx/venvs/github-backup/lib/python3.14/site-packages/github_backup/github_backup.py", line 717, in fetch_all
    response = json.loads(http_response.read().decode("utf-8"))
                          ~~~~~~~~~~~~~~~~~~^^
  File "/usr/lib/python3.14/http/client.py", line 500, in read
    s = self._safe_read(self.length)
  File "/usr/lib/python3.14/http/client.py", line 648, in _safe_read
    data = self.fp.read(cursize)
  File "/usr/lib/python3.14/socket.py", line 725, in readinto
    return self._sock.recv_into(b)
           ~~~~~~~~~~~~~~~~~~~~^^^
  File "/usr/lib/python3.14/ssl.py", line 1304, in recv_into
    return self.read(nbytes, buffer)
           ~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/ssl.py", line 1138, in read
    return self._sslobj.read(len, buffer)
           ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
ConnectionResetError: [Errno 104] Connection reset by peer
```

Author: Changaco

github_backup/github_backup.py

@@ -806,6 +806,7 @@ def _extract_legal_url(response_body_bytes):
                     response = json.loads(http_response.read().decode("utf-8"))
                     break  # Exit retry loop and handle the data returned
                 except (
+                    ConnectionError,
                     IncompleteRead,
                     json.decoder.JSONDecodeError,
                     TimeoutError,