Remove react-timer-mixin

Summary:
This mixin is no longer used!

closes https://github.com/facebook/react-native/issues/21485

Reviewed By: RSNara

Differential Revision: D10451307

fbshipit-source-id: 2315244b2f292cfff71241f95a3afcd9788d74be

package.json

@@ -191,7 +191,6 @@
     "prop-types": "^15.5.8",
     "react-clone-referenced-element": "^1.0.1",
     "react-devtools-core": "^3.4.0",
-    "react-timer-mixin": "^0.13.2",
     "regenerator-runtime": "^0.11.0",
     "rimraf": "^2.5.4",
     "semver": "^5.0.3",

yarn.lock

@@ -5385,11 +5385,6 @@ react-test-renderer@16.6.0-alpha.8af6728:
     react-is "^16.6.0-alpha.8af6728"
     scheduler "^0.10.0-alpha.8af6728"
 
-react-timer-mixin@^0.13.2:
-  version "0.13.4"
-  resolved "https://registry.yarnpkg.com/react-timer-mixin/-/react-timer-mixin-0.13.4.tgz#75a00c3c94c13abe29b43d63b4c65a88fc8264d3"
-  integrity sha512-4+ow23tp/Tv7hBM5Az5/Be/eKKF7DIvJ09voz5LyHGQaqqz9WV8YMs31eFvcYQs7d451LSg7kDJV70XYN/Ug/Q==
-
 react-transform-hmr@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/react-transform-hmr/-/react-transform-hmr-1.0.4.tgz#e1a40bd0aaefc72e8dfd7a7cda09af85066397bb"