Update set of optionally allowed expression types in no-top-level-variables configuration

[ericcornelissen]

Relates to #1107

Summary

The YieldExpression value for the allowed option of the no-top-level-variables is useless because yield is not allowed at the top level - hence it should be removed.

However, it can't just be removed because that's a breaking change because it would reject any existing configuration that does explicitly allow it.

Change description

To close this issue the ImportExpression, SequenceExpression, ThisExpression, and YieldExpression should be removed from the allowedOption.enum list.

[ericcornelissen]

Following #1166, this issue also goes for ImportExpression, SequenceExpression, and ThisExpression but instead because they're now in the list of always allowed expressions.