do not sync config on changes on main; do it only releases

[hidalgopl]

What issue type does this pull request address? (keep at least one, remove the others)
/kind enhancement

What does this pull request do? Which issues does it resolve? (use resolves #<issue_number> if possible)
removes sync-config.yaml workflows, that was copying the config/*.go contents to vcluster-config on each change.
As the result, there was potential mismatch between vcluster.schema.json & config/*.go files in vcluster-config.
Instead, we will generate vcluster.schema.json on each release & copy contents of config/*.go files on one commit.
Then, we can tag this commit with given minor version in the vcluster-config repo.

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