Fix latest commit time

[m-aciek]

Fixes #85.

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📊 Dashboard preview 📊: https://python-docs-translations.github.io/dashboard/89/merge/

[StanFromIreland]

In the build Korean has a last updated date of 2025/05/01 12:51:18, there was a new commit a short while ago (python/python-docs-ko@625f651) it would be good to test to see if it updates.

I worry rerunning may be pointless since it will ignore the saved clones I presume.

[m-aciek]

I'm convinced this PR fixes the issue. In completion.py we've been checking out a commit from month ago for majority of languages. The repositories were in detached state after that and regular git checkout wasn't enough to go back to the previous state. In this PR the state is being restored directly after it's changed.