Before, QuestyCaptcha answers were case-insensitive when there was
only one answer for a question, but they had to be lowercase when
there was an array of answers. This makes it so that when an array
of answers is provided for a question in $wgCaptchaQuestions, those
answers are case-insensitive.
Bug: T65272
Change-Id: I146b53cacf901c45ce27bd87fdf8125bfd2bc270