remove the sync script

[keewis]

follow-up to #5468. We removed the external version file but the sync script is still run in CI, which obviously fails and causes the report to be stripped from the PR comment.

For a future PR / investigation: pre-commit allows installing dependencies from the language's package index (e.g. PyPI for python), but packages installed using that method are not updated until the hook is updated / reinstalled. For blackdoc we were thinking about pinning black at some point so we could work around that by synchronizing the version with the hook version, but this is probably more work than it is worth. I guess this means we have to wait on pre-commit to fix this and in the meantime we'll probably have to tell people to clean their pre-commit caches on updates for black and numpy...

[github-actions]

Unit Test Results

         6 files  ±0           6 suites  ±0   51m 35s ⏱️ ±0s
16 172 tests ±0  14 441 ✔️ ±0  1 731 💤 ±0  0 ❌ ±0 
90 228 runs  ±0  82 077 ✔️ ±0  8 151 💤 ±0  0 ❌ ±0 

Results for commit 7f722cf. ± Comparison against base commit 7f722cf.

♻️ This comment has been updated with latest results.