Deduplicate imports after resolving in `renderModule`

[Fil]

this is not always deduplicated in exported modules:

import "../../_npm/d3@7.9.0/_esm.js";
import "../../_npm/d3@7.9.0/_esm.js";

Mike says:

it’s because we deduplicate before resolving rather than after. So here there are two global imports of D3: the chart.js module imports npm:d3, and Plot imports npm:d3@^7.9.0. These are two distinct specifiers prior to resolving, but they both resolve to npm:d3@7.9.0 after. We can fix this in renderModule.