Add separate dialog for recovery method removed

The "New Recovery Method" dialog would show if either the recovery method had
been changed or removed, but the dialog text didn't make much sense for the
removed case.

This adds a separate dialog customized for the removed case.

Fixes https://github.com/vector-im/riot-web/issues/8046.

res/css/views/dialogs/keybackup/_KeyBackupFailedDialog.scss

@@ -0,0 +1,41 @@
+/*
+Copyright 2018 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+.mx_KeyBackupFailedDialog .mx_Dialog_title {
+    margin-bottom: 32px;
+}
+
+.mx_KeyBackupFailedDialog_title {
+    position: relative;
+    padding-left: 45px;
+    padding-bottom: 10px;
+
+    &:before {
+        mask: url("../../img/e2e/lock-warning.svg");
+        mask-repeat: no-repeat;
+        background-color: $primary-fg-color;
+        content: "";
+        position: absolute;
+        top: -6px;
+        right: 0;
+        bottom: 0;
+        left: 0;
+    }
+}
+
+.mx_KeyBackupFailedDialog .mx_Dialog_buttons {
+    margin-top: 36px;
+}