Update dependency vue-loader to v15.8.3

Author: renovate-bot

package-lock.json

@@ -36,7 +36,7 @@
     "script-ext-html-webpack-plugin": "2.1.4",
     "start-server-and-test": "1.10.6",
     "vue": "2.6.11",
-    "vue-loader": "15.7.2",
+    "vue-loader": "15.8.3",
     "vue-template-compiler": "2.6.11",
     "webpack": "4.41.2",
     "webpack-cli": "3.3.10",