RFR(T): 8221434: Fix typo in lib-x11 autoconf error message about missing headers

[Gustavo Romero]

Hi David,

On 03/25/2019 09:11 PM, David Holmes wrote:
> Looks good Gustavo.

Thanks a lot for the quick review.

Pushed to jdk/jdk since it's a trivial change.

Best regards,
Gustavo