chore(deps): update dependency sinon to v7 (#321)

Author: renovate[bot]

handwritten/bigtable/package.json

@@ -101,7 +101,7 @@
     "power-assert": "^1.4.4",
     "prettier": "^1.7.4",
     "proxyquire": "^2.0.0",
-    "sinon": "^6.0.0",
+    "sinon": "^7.0.0",
     "uuid": "^3.0.1"
   }
 }