feat(docs): fix feeOut calculation example and unify calculation format

[YauheniPratasau]

Summary

Fixed an incorrect example in the "swapVAIForStable (If the oracle price of the paired stablecoin is above $1)" paragraph.

Details

The previous documentation stated that the user would provide 11.1 VAI when feeOut = 10%, but the correct amount should be 12.1 VAI.

Correct calculation

• Oracle price: 1 USDT = $1.1
• Desired amount: 10 USDT
• Conversion rate: max(1, 1.1) = 1.1 VAI per USDT
• Principal: 10 × 1.1 = 11 VAI
• Fee (10%): 11 × 0.1 = 1.1 VAI
• Total = 12.1 VAI

Changes

• Corrected the total amount from 11.1 VAI → 12.1 VAI
• Unified the calculation format across multiple examples to the same clear style: 11 VAI (10 USDT * 1.1 $/USDT) + fees