message: fix(popover): markup for bs4
diff: <div class="row panel" style="position: relative; overflow: hidden;">
  - <div class="card panel-body">
  + <div class="card-block panel-body">
  <button type="button" class="btn btn-danger"
  popover="Vivamus sagittis lacus vel augue laoreet rutrum faucibus.">
  Default popover
  