Use json-rpc-engine@5.1.8 (#8124)

package.json

@@ -113,7 +113,7 @@
     "gaba": "^1.9.3",
     "human-standard-token-abi": "^2.0.0",
     "jazzicon": "^2.0.0",
-    "json-rpc-engine": "^5.1.6",
+    "json-rpc-engine": "^5.1.8",
     "json-rpc-middleware-stream": "^2.1.1",
     "jsonschema": "^1.2.4",
     "lodash": "^4.17.15",

yarn.lock

@@ -16624,17 +16624,7 @@ json-rpc-engine@^3.4.0, json-rpc-engine@^3.6.0:
     promise-to-callback "^1.0.0"
     safe-event-emitter "^1.0.1"
 
-json-rpc-engine@^5.1.3, json-rpc-engine@^5.1.5, json-rpc-engine@^5.1.6:
-  version "5.1.6"
-  resolved "https://registry.yarnpkg.com/json-rpc-engine/-/json-rpc-engine-5.1.6.tgz#3823c1e227657ac5f22a36351db5bb76fa70cf38"
-  integrity sha512-9nDeIIu6o7cvzWRrHNuNi+TiGe+YWOp3ZQkHtpPnQzXuX8Y5ZU2Oot3FDI+DaQyXIqQ6SjtM6rixDOJTjjA8NA==
-  dependencies:
-    async "^2.0.1"
-    eth-json-rpc-errors "^2.0.0"
-    promise-to-callback "^1.0.0"
-    safe-event-emitter "^1.0.1"
-
-json-rpc-engine@^5.1.8:
+json-rpc-engine@^5.1.3, json-rpc-engine@^5.1.5, json-rpc-engine@^5.1.8:
   version "5.1.8"
   resolved "https://registry.yarnpkg.com/json-rpc-engine/-/json-rpc-engine-5.1.8.tgz#5ba0147ce571899bbaa7133ffbc05317c34a3c7f"
   integrity sha512-vTBSDEPJV1fPAsbm2g5sEuPjsgLdiab2f1CTn2PyRr8nxggUpA996PDlNQDsM0gnrA99F8KIBLq2nIKrOFl1Mg==