Remove `sharp` from `allowBuilds`

[maiertech]

Sharp is not a direct dependency. Need to wait until it shows up as at least v0.35.0 in the lockfile.

See https://mu.social/profile/sebastienlorber.com/post/3monfditakk2p.

[maiertech]

We need to wait for a stable @sveltejs/enhanced-img release that updates its Sharp dependency to >=0.35.0. The current stable release (0.11.0) still resolves sharp@0.34.5, which requires build approval. Once the lockfile resolves Sharp 0.35 or newer, remove sharp: true from pnpm-workspace.yaml and verify installation and CI.