chore: remove check for existing tokens

[JDawg287]

Description

This PR removes the check for External ERC20 token addresses when deploying an ERC20 token via the Topos Cross-Subnet Messaging Protocol.
Only Internal tokens are allowed to be deployed.

Fixes TP-782

Additions and Changes

• Removed the address param from the input params for the sendToken method in ERC20Messaging.sol smart contract
• Adapted the unit tests to the changes

Breaking Changes

Changes the input params for the deployToken function so will require changes to the infra as well

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[sebastiendan]

Passing CI with the related Frontend update
https://github.com/topos-protocol/e2e-tests/actions/runs/6958443031