EuiSuperSelect's options prop isn't marked as required in docs

[chandlerprall]

EuiSuperSelect's options prop has isRequired, but react-docgen doesn't appear to notice that when generating documentation.

[thompsongl]

Looks like if you provide a defaultProp value, react-docgen will mark said prop as not required¹ . Which...is arguably correct, and regardless brings up a better point about the EuiSuperSelect component definition.

We should remove the defaultProp value for options ([]) as it still results in a TypeError² and that TypeError is less helpful than the failed prop type warning from React.

[1] reactjs/react-docgen#321 (comment)
[2] TypeError: Cannot read property 'inputDisplay' of undefined