Correct regex pattern for case-insensitive match

Updated the regex pattern in `StaffAppFormData.java` to ensure that the "yes" or "no" answers are case-insensitive. This improves the form validation to accept "Yes", "YES", "No", or "NO" without errors.

src/main/java/com/alttd/forms/controlers/apply/StaffAppFormData.java

@@ -45,7 +45,7 @@ public class StaffAppFormData extends Form {
 
     @NotEmpty(message = "An answer is required")
     @Length(min = 2, max = 3, message = "Please answer yes or no")
-    @Pattern(regexp = "(yes|no)$", message = "Yes or no")
+    @Pattern(regexp = "(?i)^(yes|no)$", message = "Yes or no")
     public final String pc_requirements;
 
     @Min(value = 0, message = "Please enter a valid age")