fix: packages/abi-gen/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ELLIPTIC-8187303

packages/abi-gen/package.json

@@ -64,7 +64,7 @@
     "dependencies": {
         "@0x/types": "^3.2.0",
         "@0x/typescript-typings": "^5.1.1",
-        "@0x/utils": "^5.5.1",
+        "@0x/utils": "^6.4.0",
         "@types/toposort": "^2.0.1",
         "chalk": "^2.3.0",
         "change-case": "^3.0.2",
@@ -81,12 +81,12 @@
     },
     "devDependencies": {
         "@0x/assert": "^3.0.9",
-        "@0x/base-contract": "^6.2.3",
+        "@0x/base-contract": "^7.0.0",
         "@0x/contracts-gen": "^2.0.10",
-        "@0x/dev-utils": "^3.3.0",
+        "@0x/dev-utils": "^5.0.0",
         "@0x/json-schemas": "^5.1.0",
         "@0x/sol-compiler": "^4.1.1",
-        "@0x/subproviders": "^6.1.1",
+        "@0x/subproviders": "^7.0.0",
         "@0x/tslint-config": "^4.1.0",
         "@0x/web3-wrapper": "^7.2.0",
         "@types/glob": "5.0.35",
@@ -99,7 +99,7 @@
         "chai-as-promised": "^7.1.0",
         "chai-bignumber": "^3.0.0",
         "dirty-chai": "^2.0.1",
-        "ethers": "~4.0.4",
+        "ethers": "~5.0.0",
         "make-promises-safe": "^1.1.0",
         "mocha": "^6.2.0",
         "npm-run-all": "^4.1.2",