Update dependency chai to v4.3.7

Author: renovate[bot]

package-lock.json

@@ -19,7 +19,7 @@
     "@vue/cli-plugin-unit-mocha": "4.4.4",
     "@vue/test-utils": "1.0.0-beta.25",
     "axios": "0.18.1",
-    "chai": "4.2.0",
+    "chai": "4.3.7",
     "coffee-loader": "0.9.0",
     "coffeescript": "2.3.2",
     "stylus": "0.54.5",