fix: UNQ transfers from Unique Network to Astar

[mrshiposha]

Pull Request Summary

Fix transfer of UNQ from Unique Network to Astar.

Check list

• contains breaking changes
• adds new feature
• modifies existing feature (bug fix or improvements)
• relies on other tasks
• documentation changes
• tested on mobile devices

This pull request makes the following changes:

Fixes

Fixed xtokens.transfer currency ID argument.

Here is the link to astar-apps with the fix already applied: https://poc-apps.aku.uniquenetwork.dev/astar/assets.
20 UNQ was transferred using the astar-apps version from the link above. Subscan XCM Transfer Info.

The fix is required following the v10030070 Unique Network upgrade, which uses the collection ID type directly as CurrencyId.

The collection ID for the native asset (UNQ) is 0.

[impelcrypto]

LGTM. I've tested and it worked.

[gluneau]

LGTM