fix storybook build (pnpm -C web dev)

[beyang]

For reasons I don't fully understand, these imports were causing the storybook build (pnpm -C web dev) to fail. It looks like the re-exported symbols in question (modelsService, CodyClientConfig) were stripped but then later expected from within Storybook, which caused errors like this:

Uncaught SyntaxError: The requested module '/@fs/home/beyang/src/github.com/sourcegraph/cody/lib/shared/src/models/modelsService.ts' does not provide an export named 'ModelCategory' (at index.ts:7:5)

Test plan

Dev-only