Removed legacy wallets from Wallet FAQ section

[TinaKT]

Purpose

The purpose of the pull request is to remove references and links to legacy wallets.

Changes

Deleted Concordium Wallet for Mobile FAQ
Updated:

• Wallet FAQs
• CryptoX Concordium Wallet FAQ (Note: I kept info about migrating from legacy wallet to CryptoX in this page)
• Deciding between the wallets
• Accounts (I hade overlooked one mention of legacy wallet in previous PR)

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• [x I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.

By submitting the contribution I accept the terms and conditions of the
Contributor License Agreement v1.0

• link: https://developers.concordium.com/CLAs/Contributor-License-Agreement-v1.0.pdf

[dragosgd]

LGTM