fix: display swap button in top assets only on hover

[compojoom]

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What it solves

Display the swap button only on hover in the "top asset" block. @TanyaEfremova @kirkkonen looks a bit weird or like a bug, because we have this space on the right now without the button.

Screenshots

Checklist

• [ ] I've tested the branch on mobile 📱
• [ ] I've documented how it affects the analytics (if at all) 📊
• [ ] I've written a unit/e2e test for it (if applicable) 🧑‍💻