Remove explicit import of lru-cache workaround

[peterpeterparker]

Motivation

Following build reproducibility improvements resulting of #2584, #2574 and #2562, I think we do not need the explicit import of lru-cache workaround anymore.

I ran the ./script/test-reproducibility script which seems fine.

WDYT @dskloetd ?

[dskloetd]

If I remember correctly, I was not able to reproduce the issue solved by this import locally but investigated it based on CI runs.
If we want to try this, we'll have to check with scripts/nns-dapp/ci-consistency after a while.
I'd rather first have a clean record following our recent effort.

[peterpeterparker]

Sure works for me, let's postpone.
I'll keep the PR in a draft, ultimately I'm happy if we can remove explicit import at the root of the app.