build(deps): bump gitpython from 3.1.50 to 3.1.57

Bumps [gitpython](https://github.com/gitpython-developers/GitPython) from 3.1.50 to 3.1.57.
- [Release notes](https://github.com/gitpython-developers/GitPython/releases)
- [Changelog](https://github.com/gitpython-developers/GitPython/blob/main/CHANGES)
- [Commits](gitpython-developers/GitPython@3.1.50...3.1.57)

---
updated-dependencies:
- dependency-name: gitpython
  dependency-version: 3.1.57
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gitopscli/git_api/git_repo.py

@@ -133,7 +133,10 @@ def get_author_from_last_commit(self) -> str:
 
     def __remote_branch_exists(self, branch: str) -> bool:
         repo = self.__get_repo()
-        return bool(repo.git.ls_remote("--heads", "origin", f"refs/heads/{branch}").strip() != "")
+        result = repo.git.ls_remote("--heads", "origin", f"refs/heads/{branch}")
+        if isinstance(result, str):
+            return result.strip() != ""
+        return bool(result)
 
     def __delete_tmp_dir(self) -> None:
         if self.__tmp_dir: