fix levit timm conversion file
# What does this PR do?
Fixes conversion file `convert_levit_timm_to_pytorch.py` for levit


Fixes # (issue)
https://github.com/huggingface/transformers/issues/20937




## Who can review?
@NielsRogge



_The documentation is not available anymore as the PR was closed or merged._<|||||>Thanks again for your contribution!