Add rubocop rule for enable_lock_retries

What does this MR do and why?

This change adds a Rubocop rule to prevent using disable_ddl_transaction! and enable_lock_retries! within the same migration. These 2 things should not be used together because enable_lock_retries! hooks into ddl_transaction to trigger the retrying but with disable_ddl_transaction! this code is never executed and nothing is retried.

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