fix(query-generator): make it possible to use Op as comparator in Seq…

[jharting]

…uelize.where (#9123)

Closes #9123

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• Does npm run test or npm run test-DIALECT pass with this change (including linting)?
• Does the description below contain a link to an existing issue (Closes #[issue]) or a description of the issue you are solving?
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Description of change

make it possible to use Op operators in Sequelize.where, e.g.:

sequelize.where(sequelize.fn('SUM', sequelize.col('price')), Op.gt, 0);

[codecov]

Codecov Report

Merging #9124 into master will increase coverage by <.01%.
The diff coverage is 100%.

[eseliger]

We could leave one example in the docs on that :)