Remove eslint-plugin-flow-vars. (#2842)

* Remove `eslint-plugin-flow-vars`.

* Put `testMatch` back on a single line.  How did that even happen?

Author: wtgtybhertgeghgtwtg

package.json

@@ -12,7 +12,6 @@
     "codecov": "^1.0.1",
     "eslint": "^3.11.1",
     "eslint-plugin-babel": "^4.0.0",
-    "eslint-plugin-flow-vars": "^0.5.0",
     "eslint-plugin-flowtype": "^2.28.2",
     "eslint-plugin-react": "^6.7.1",
     "flow-bin": "^0.37.4",