metro-bundler: remove image-size

Summary:
It appears this is not needed to build or anything, only for metro-bundler itself.

Closes https://github.com/facebook/metro-bundler/issues/20.

Reviewed By: cpojer

Differential Revision: D5370513

fbshipit-source-id: 563b5716ca9ab1b58fc7ae1f757efc61cf946168

package.json

@@ -24,7 +24,6 @@
     "eslint-plugin-react": "^7.0.1",
     "flow-bin": "^0.48.0",
     "glob": "^7.1.1",
-    "image-size": "^0.5.1",
     "istanbul-api": "^1.1.0",
     "istanbul-lib-coverage": "^1.0.0",
     "jest": "^19.0.2",

yarn.lock

@@ -1910,10 +1910,6 @@ ignore@^3.2.0:
   version "3.3.3"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.3.3.tgz#432352e57accd87ab3110e82d3fea0e47812156d"
 
-image-size@^0.5.1:
-  version "0.5.5"
-  resolved "https://registry.yarnpkg.com/image-size/-/image-size-0.5.5.tgz#09dfd4ab9d20e29eb1c3e80b8990378df9e3cb9c"
-
 imurmurhash@^0.1.4:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/imurmurhash/-/imurmurhash-0.1.4.tgz#9218b9b2b928a238b13dc4fb6b6d576f231453ea"