Regex fixed, no more undercase letters

web/template/home.gohtml

@@ -567,7 +567,7 @@
                         </section>
                     </template>
                     <template x-if="plannedStreams.hasElements()">
-                        <section x-data="{isLectureHallValid(lectureHall) {const regex = /^\d{4}\.[A-Za-z0-9]{2}\.[A-Za-z0-9]{3,4}$/;
+                        <section x-data="{isLectureHallValid(lectureHall) {const regex = /^\d{4}\.[A-Z0-9]{2}\.[A-Z0-9]{3,4}$/;
                             return regex.test(lectureHall);}}"
                                  class="tum-live-course-view-item px-3">
                             <header>