Fix the copy button (when copying snippets)

[NullVoxPopuli]

The copy button previously included the copy menu (but not the copy button).

This work now also excludes the copy menu.

[stackblitz]

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[github-actions]

Project	Preview URL1	Manage
Limber	https://fix-copy-button.limber-glimdown.pages.dev	on Cloudflare
Tutorial	https://fix-copy-button.limber-glimmer-tutorial.pages.dev	on Cloudflare

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Footnotes

1. if these branch preview links are not working, please check the logs for the commit-based preview link. There is a character limit of 28 for the branch subdomain, as well as some other heuristics, described here for the sake of implementation ease in deploy-preview.yml, that algo has been omitted. The URLs are logged in the wrangler output, but it's hard to get outputs from a matrix job. ↩