web-wallet: Fix build warning for unused icon

[nortonandreev]

Resolves #1632

[ascartabelli]

Left a couple of notes.
This effectively solves the problem, thanks, as it was annoying.
I think we need to understand better why the build system sees a problem here.

One last thought: should we remove the components-showcase from the production build altogether?

[nortonandreev]

One last thought: should we remove the components-showcase from the production build altogether?

I think this would make sense to do, once we have the Duskit library with a publicly accessible components showcase (and once we have migrated to use it across the project).

I think it's useful to have the design language / system publicly accessible so that the stakeholders can have a quick look easily. Like, for example, if Giancarlo wanted a preview of the way all the Button variants were implemented in the code.