lisk-transaction:validation:schema senderId, recipientId are not required and senderSecondPublicKey is an invalid property - Closes #1121

[pablitovicente]

What was the problem?

Schema validation was expecting recipentId, SenderId and validating secondPublicKey which were invalid

How did I fix it?

Removing said fields from schema

How to test it?

• Build should be green
• Try to register a multi-signature transaction and should be possible

Review checklist

• The PR resolves lisk-transaction:validation:schema senderId, recipientId are not required and senderSecondPublicKey is an invalid property #1121
• All new code is covered with unit tests
• All new code was formatted with Prettier
• Linting passes
• Tests pass
• Commit messages follow the commit guidelines
• Documentation has been added/updated