bootstrap: Remove legacy nav nav-list classes and related CSS.

With the redesign of all popovers completed, we have transitioned away
from the legacy Bootstrap-based popover system. As a result, the
Bootstrap `nav nav-list` classes are now obsolete and no longer used
in the codebase.

This commit, a part of the efforts to clean up the legacy Bootstrap CSS,
removes these unused classes and any related CSS workarounds.

Fixes #26990.

web/styles/dark_theme.css

@@ -660,8 +660,6 @@
     }
 
     & .drafts-container .drafts-header,
-    .nav > li > a:focus,
-    .nav > li > a:hover,
     .subscriptions-container .subscriptions-header,
     .user-groups-container .user-groups-header,
     .overlay-messages-header,
@@ -719,10 +717,6 @@
         color: inherit;
     }
 
-    .nav-list > li > a {
-        text-shadow: none;
-    }
-
     #message-edit-history-overlay-container {
         .message_edit_history_content {
             .highlight_text_inserted {

web/styles/popovers.css

@@ -21,17 +21,6 @@
         margin: 5px 0;
     }
 
-    /* TODO: Clean this logic up after drop Bootstrap styling */
-    & ul.nav {
-        /* Override default padding of tippyjs */
-        margin: 0 -9px;
-
-        /* Override bootstrap defaults */
-        .nav-list > li > a {
-            padding: 3px 15px;
-        }
-    }
-
     &[data-placement^="top"] {
         > .tippy-arrow {
             &::before {
@@ -755,11 +744,6 @@ ul.popover-group-menu-member-list {
            we can ignore the colors applied from `tippy-box`. */
         color: var(--color-text-default);
     }
-
-    & ul.nav {
-        /* TODO: Clean this logic up after drop Bootstrap styling */
-        margin: 0;
-    }
 }
 
 .emoji-popover-root {

web/third/bootstrap/css/bootstrap.app.css

@@ -159,76 +159,6 @@ input:focus:invalid:focus {
   -moz-box-shadow: 0 0 6px #f8b9b7;
   box-shadow: 0 0 6px #f8b9b7;
 }
-.nav {
-  margin-left: 0;
-  margin-bottom: 20px;
-  list-style: none;
-}
-.nav > li > a {
-  display: block;
-}
-.nav > li > a:hover,
-.nav > li > a:focus {
-  text-decoration: none;
-  background-color: #eeeeee;
-}
-.nav > li > a > img {
-  max-width: none;
-}
-.nav-list {
-  padding-left: 15px;
-  padding-right: 15px;
-  margin-bottom: 0;
-}
-.nav-list > li > a {
-  margin-left: -15px;
-  margin-right: -15px;
-  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.5);
-}
-.nav-list > li > a {
-  padding: 3px 15px;
-}
-.nav-list > .active > a,
-.nav-list > .active > a:hover,
-.nav-list > .active > a:focus {
-  color: #ffffff;
-  text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.2);
-  background-color: #0088cc;
-}
-.nav-list .divider {
-  height: 1px;
-  margin: 9px 1px;
-  overflow: hidden;
-  background-color: #e5e5e5;
-  border-bottom: 1px solid #ffffff;
-}
-.nav > .dropdown.active > a:hover,
-.nav > .dropdown.active > a:focus {
-  cursor: pointer;
-}
-.nav > li.dropdown.open.active > a:hover,
-.nav > li.dropdown.open.active > a:focus {
-  color: #ffffff;
-  background-color: #999999;
-  border-color: #999999;
-}
-.nav li.dropdown.open .caret,
-.nav li.dropdown.open.active .caret,
-.nav li.dropdown.open a:hover .caret,
-.nav li.dropdown.open a:focus .caret {
-  border-top-color: #ffffff;
-  border-bottom-color: #ffffff;
-  opacity: 1;
-}
-.nav > .disabled > a {
-  color: #999999;
-}
-.nav > .disabled > a:hover,
-.nav > .disabled > a:focus {
-  text-decoration: none;
-  background-color: transparent;
-  cursor: default;
-}
 .close {
   float: right;
   font-size: 20px;