feat!: remove Go and Rust function templates (#7957)

#### Summary

**BREAKING:** Remove Go and Rust templates from `netlify
functions:create` command.

These are rarely used and not worth maintaining here.

Go and Rust functions are still supported; this only removes templates
from the CLI.

---
[Slack
Thread](https://netlify.slack.com/archives/C096B91TE03/p1771449094377079?thread_ts=1771449094.377079&cid=C096B91TE03)

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>

Author: serhalp