[@loopback/sequelize] Typescript error when using the "required" property with Sequelize

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### Describe the bug

When trying to use the new "required: true" to use an Inner Join instead of a Left Join, it leads to a Typescript error:
```
Type '{ relation: string; scope: { where: { id: number; }; }; required: true; }'
is not assignable to type 'InclusionFilter'.
Object literal may only specify known properties, and 'required'
does not exist in type 'Inclusion'.

53 required: true
```

This also happens for nested relation operations such as:
```
myRepository(foreignKey).find({
include: [
{
// ...
required: true
}
]
}
```

### Logs

_No response_

### Additional information


### Reproduction

https://codesandbox.io/p/devbox/loopback-sequelize-types-24l36w

Start with the linked CodeSandbox reproduction and inspect the InclusionFilter and Inclusion types involved in the TypeScript error. Confirm how the Sequelize extension represents nested includes, then verify that required: true is accepted and the reproduction compiles for both relation operations.

Written by the indexing model from the issue text.