Fix: Upgrade react-docgen to 3.0.0-rc.2 (#1200)

Closes #1177

Author: macintoshhelper

package-lock.json

@@ -74,7 +74,7 @@
     "q-i": "^2.0.1",
     "react-codemirror2": "^5.1.0",
     "react-dev-utils": "^6.0.5",
-    "react-docgen": "3.0.0-beta12",
+    "react-docgen": "3.0.0-rc.2",
     "react-docgen-annotation-resolver": "^1.0.0",
     "react-docgen-displayname-handler": "^2.1.0",
     "react-group": "^1.0.6",

package.json

@@ -137,7 +137,7 @@ exports[`PropsRenderer should render parameters 1`] = `
             Object {
               "description": "Description",
               "name": "value",
-              "optional": undefined,
+              "optional": false,
               "type": Object {
                 "name": "Number",
               },