Update dependency bootstrap-vue to v2.21.0

Author: renovate-bot

frontend/package-lock.json

@@ -15,7 +15,7 @@
   "dependencies": {
     "axios": "0.21.0",
     "bootstrap": "4.5.3",
-    "bootstrap-vue": "2.20.1",
+    "bootstrap-vue": "2.21.0",
     "jquery": "3.5.1",
     "core-js": "3.8.1",
     "vue": "2.6.12",