Fix jsen tests for TS 3.9 (#44161)
Fix jsen tests for TS 3.9 (#44161)

TS 3.9 forbids deleting a property that isn't marked optional or
undefined. jsen's tests do this in order to test before/after `greedy`
is set, but because the options object doesn't have a type annotation,
the compiler doesn't know that `greedy` is optional. I added the type
annotation.
dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,markogresak/DefinitelyTyped,mcliment/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped