Fix Arel deprecations
What does this MR do?
Fix some deprecation warning that I see running the migration helper specs. Related to #28497 (closed)
DEPRECATION WARNING: Dangerous query method (method whose arguments are
used as raw SQL) called with non-attribute argument(s).
Non-attribute arguments will be disallowed in Rails 6.0.
This method should not be called with user-provided values, such as
request parameters or model attributes. Known-safe values can be passed
by wrapping them in Arel.sql().