Remove unused module vue-demi

Author: pascalseeland

viplab-standalone-frontend-vue/package-lock.json

@@ -41,7 +41,6 @@
     "vtk.js": "^26.0.0",
     "vue": "~2.6.0",
     "vue-blockui": "^1.1.7",
-    "vue-demi": "^0.11.3",
     "vue-easy-dnd": "^1.19.0",
     "vue-prism-editor": "^1.2.2",
     "vue-router": "^3.5.2",