cleanup: remove vestigial kodata directories

The kodata directories contained symlinks to .git/HEAD, .git/refs, and
the repo root LICENSE. These were used by the old knative.dev/pkg/changeset
package to embed git revision info into container images at build time.

That package now uses Go's built-in debug.ReadBuildInfo() / vcs.revision
instead, and no code reads these kodata files. Additionally, ko v0.10+
rejects symlinks that resolve outside the kodata root, so these symlinks
block upgrading setup-ko from v0.9 to v0.10.

Author: creydr