Update dependency popper.js to v2

Author: renovate-bot

src/main/resources/templates/login.html

@@ -57,7 +57,7 @@ <h1>Custom Login page</h1>
     ================================================== -->
     <!-- Placed at the end of the document so the pages load faster -->
     <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
-    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/2.11.0/umd/popper.min.js" integrity="sha512-PZrlUFhlOigX38TOCMdaYkhiqa/fET/Lztzjn+kdGxefUZanNUfmHv+9M/wSiOHzlcLX/vcCnmvOZSHi5Dqrsw==" crossorigin="anonymous"></script>
     <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js" integrity="sha384-smHYKdLADwkXOn1EmN1qk/HfnUcbVRZyYmZ4qpPea6sjB/pTJ0euyQp0Mk8ck+5T" crossorigin="anonymous"></script>
 </body>
 </html>