sql: reenable decimal in query-comparison-oracle

The decimal type was disabled in query-comparison-oracle due to https://github.com/cockroachdb/cockroach/issues/88547. We were discussing in a collab session that it would improve our test coverage to reenable this type. We looked through some of the old issues and think that the errors may have to do with decimal precision due to the presence of division operators in the queries, however this will require some more investigation.

Jira issue: CRDB-27952

Locate the query-comparison-oracle test and inspect the change that disabled decimal because of issue 88547. Run the relevant comparison tests, investigate whether division causes decimal-precision errors, and consider the work done when decimal is reenabled with the test coverage passing.

Written by the indexing model from the issue text.