docs: remove Star History graph from README

[vycdev]

Summary

Remove the ## Star History section and its linked chart from README.md.

Why

GitHub changed the API access used by the embedded Star History chart, and the graph no longer works without supplying a GitHub token. Kromacut should not need or maintain a token just to render a README graph, so the broken integration should be removed.

Scope

• Remove the ## Star History heading.
• Remove the linked star-history.com chart directly below it.
• Keep the surrounding release documentation and ## Contributing section intact.
• Avoid unrelated README changes.

Acceptance criteria

• README.md no longer contains the Star History section.
• No star-history.com URL remains in the README.
• The README still renders cleanly, with normal spacing before ## Contributing.
• No application code or behavior is changed.

This should be a straightforward first contribution; no build or test run is expected for this documentation-only change.

[vycdev]

Update: PR #70 found a working tokenless replacement, so I am keeping the Star History section and using Mubelotix's hosted instance at https://star-history.dera.page for now.

Longer term, I plan to host my own instance so Kromacut is not permanently dependent on a third-party deployment. PR #70 has been merged into develop and resolves this issue with that interim approach.

Thanks @Mubelotix for the fix.