Update dependency bignumber.js to v9.1.2

Author: renovate[bot]

REPOS/mysql/package.json

@@ -13,7 +13,7 @@
   ],
   "repository": "mysqljs/mysql",
   "dependencies": {
-    "bignumber.js": "9.0.0",
+    "bignumber.js": "9.1.2",
     "readable-stream": "2.3.7",
     "safe-buffer": "5.1.2",
     "sqlstring": "2.3.2"