bug: `wkg fetch` will attempt workspace fetching even if a member manifest is present

[mkatychev]

wasm-pkg-tools/crates/wkg/src/wit.rs

Lines 180 to 186 in dfa2e17

	match root {
	Some(root) => {
	self.run_workspace_fetch(&dirs, output, &manifest, root)
	.await
	}
	None => self.fetch_into_lock(&dirs, &manifest, output).await,
	}

This will always call run_workspace_fetch if one can path to an ancestor manifest that is a workspace.