fixed deprecated warnings

refilc_mobile_ui/lib/common/widgets/missed_exam/missed_exam_tile.dart

@@ -23,7 +23,7 @@ class MissedExamTile extends StatelessWidget {
             height: 36,
             child: Icon(
               FeatherIcons.slash,
-              color: AppColors.of(context).red.withOpacity(.75),
+              color: AppColors.of(context).red.withValues(alpha: .75),
               size: 28.0,
             )),
         title: Text("missed_exams"

refilc_mobile_ui/lib/common/widgets/missed_exam/missed_exam_view.dart

@@ -50,7 +50,7 @@ class MissedExamViewTile extends StatelessWidget {
           leading: Icon(
             SubjectIcon.resolveVariant(
                 subject: lesson.subject, context: context),
-            color: AppColors.of(context).text.withOpacity(.8),
+            color: AppColors.of(context).text.withValues(alpha: .8),
             size: 32.0,
           ),
           title: Text(