chore(deps): update dependency mocha to v7 (#767)

Author: renovate[bot]

packages/opencensus-core/package-lock.json

@@ -53,7 +53,7 @@
   },
   "devDependencies": {
     "@types/continuation-local-storage": "^3.2.1",
-    "@types/mocha": "^5.2.5",
+    "@types/mocha": "^7.0.0",
     "@types/node": "^10.12.12",
     "@types/once": "^1.4.0",
     "@types/semver": "^6.0.0",
@@ -62,7 +62,7 @@
     "codecov": "^3.6.2",
     "gts": "^1.0.0",
     "intercept-stdout": "^0.1.2",
-    "mocha": "^6.1.0",
+    "mocha": "^7.0.0",
     "nyc": "14.1.1",
     "ts-mocha": "^6.0.0",
     "ts-node": "^8.0.0",