Switch to @jridgewell/sourcemap-codec to avoid deprecation warnings in libraries that depend on sorcery

[falynx]

Hi Rich, you deprecated sourcemap-codec in favor of @jridgewell/sourcemap-codec. svelte-preprocess currently depends on this sorcery library, which results in a deprecation warning.

$ pnpm up --latest
 WARN  deprecated sourcemap-codec@1.4.8: Please use @jridgewell/sourcemap-codec instead
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[Rich Harris]

This was fixed in 15e2b23