Bump and consolidate dependencies

This commit bumps and consolidates several transitive dependencies:
* ajv `6.12.2`
* har-validator `5.1.3`
* request `2.88.2`
* schema-utils `1.0.0`

Note: an older version of ajv and schema-utils are each still
present because they are included in dev dependencies. I opted not
to attempt to update these.

package.json

@@ -90,11 +90,13 @@
     "**/graphql-toolkit/lodash": "^4.17.15",
     "**/hoist-non-react-statics": "^3.3.2",
     "**/isomorphic-git/**/base64-js": "^1.2.1",
+    "**/istanbul-instrumenter-loader/schema-utils": "1.0.0",
     "**/image-diff/gm/debug": "^2.6.9",
     "**/load-grunt-config/lodash": "^4.17.20",
     "**/react-dom": "^16.12.0",
     "**/react": "^16.12.0",
     "**/react-test-renderer": "^16.12.0",
+    "**/request": "^2.88.2",
     "**/deepmerge": "^4.2.2",
     "**/fast-deep-equal": "^3.1.1"
   },