Update tx queue memo filtering

[sisuresh]

Description

Resolves #X

Checklist

• Reviewed the contributing document
• Rebased on top of master (no merge commits)
• Ran clang-format v8.0.0 (via make format or the Visual Studio extension)
• Compiles
• Ran all tests
• If change impacts performance, include supporting evidence per the performance document

[Copilot]

Pull Request Overview

This PR updates transaction queue memo filtering for Soroban transactions by simplifying the validation logic. The change removes the complex source account authentication checking and instead applies a blanket restriction on memos and muxed accounts for all Soroban invoke host function operations.

Key changes:

• Simplifies memo validation logic by removing source account authentication type checking
• Updates corresponding test expectations to reflect stricter validation

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/herder/TransactionQueue.cpp	Removes complex authentication type checking and simplifies memo/muxed account validation for Soroban transactions
src/herder/test/TransactionQueueTests.cpp	Updates test expectation from ADD_STATUS_PENDING to ADD_STATUS_ERROR to match new validation behavior

[Copilot]

This change modifies transaction validation logic that could affect fee bump transactions. Should we add or update tests for fee bump transactions to ensure they still work correctly with this new memo filtering behavior?