Add voice broadcast seek 30s forward/backward buttons (#9592)

res/css/views/elements/_AccessibleButton.pcss

@@ -111,6 +111,10 @@ limitations under the License.
         color: $accent;
     }
 
+    &.mx_AccessibleButton_kind_secondary_content {
+        color: $secondary-content;
+    }
+
     &.mx_AccessibleButton_kind_danger {
         color: $button-danger-fg-color;
         background-color: $alert;