Update vue to 2.7.8

Signed-off-by: Vincent Petry <vincent@nextcloud.com>

Author: PVince81

package-lock.json

@@ -88,7 +88,7 @@
     "url-search-params-polyfill": "^8.1.1",
     "v-click-outside": "^3.2.0",
     "v-tooltip": "^2.1.3",
-    "vue": "^2.6.14",
+    "vue": "^2.7.8",
     "vue-click-outside": "^1.1.0",
     "vue-clipboard2": "^0.3.3",
     "vue-infinite-loading": "^2.4.5",