ui: Fix placement of tags menu under tags input with Bootstrap 5

- During the placement computation for the drop down menu, the height of the
dropdown-menu is very high and that leads to it getting placed at the top of the
page instead of the below the search element.

- To avoid the problem, cap the height of the dropdown. Somehow, the original
calculation for the height using CSS calc() does not seem to working as
expected.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

plinth/templates/apps.html

@@ -28,7 +28,7 @@
                  data-bs-toggle="dropdown" aria-haspopup="true" aria-expanded="false"
                  autocomplete="off" placeholder="{% trans "Search with tags" %}">
           <div class="dropdown-menu" aria-labelledby="add-tag-input">
-            <ul class="dropdown-items list-unstyled">
+            <ul class="dropdown-items">
               {% for tag in all_tags %}
                 {% if tag not in tags %}
                   <li class="dropdown-item" data-tag="{{ tag }}"

static/themes/default/css/main.css

@@ -379,8 +379,13 @@ html {
 
 /* dropdown-menu for tags is a scrollable list */
 .tag-input .dropdown-menu {
-    bottom: calc(-100% - 10px);
     overflow-y: auto;
+    max-height: 15rem;
+}
+
+.tag-input .dropdown-menu > ul {
+    list-style: none;
+    margin-bottom: 0;
 }
 
 @media (min-width: 768px) {