Update dependency @0x/subproviders to v6

Author: renovate-bot

packages/shared/package.json

@@ -3,7 +3,7 @@
   "version": "1.0.0",
   "main": "src/index.js",
   "dependencies": {
-    "@0x/subproviders": "^5.0.4",
+    "@0x/subproviders": "^6.0.0",
     "@0x/utils": "^4.5.2",
     "@0x/web3-wrapper": "^6.0.13",
     "lodash": "^4.17.15"