Fix python version parsing (#1058)

Get python version using the stem function from `pathlib` instead of list slicing.
With list slicing assertion fails while using `pyenv` because the path is wrong

gef.py

@@ -11397,7 +11397,7 @@ def target_remote_posthook():
  pyenv = which("pyenv")
  pyenv_root = gef_pystring(subprocess.check_output([pyenv, "root"]).strip())
  pyenv_version = gef_pystring(subprocess.check_output([pyenv, "version-name"]).strip())
- site_packages_dir = pathlib.Path(pyenv_root) / f"versions/{pyenv_version}/lib/python{pyenv_version[:3]}/site-packages"
+ site_packages_dir = pathlib.Path(pyenv_root) / f"versions/{pyenv_version}/lib/python{pathlib.Path(pyenv_version).stem}/site-packages"
  assert site_packages_dir.is_dir()
  site.addsitedir(str(site_packages_dir.absolute()))
  except FileNotFoundError: