Remove duplicate flow ignore

Summary:
Added this as part of a random PR to get flow passing. This collides with a similar fix by bvaughn so let's remove mine. Also I messed up and there is a + at the start of the line :o
Closes facebook#13103

Differential Revision: D4761349

fbshipit-source-id: 0abde66a1ac4c185bbd7142ecd800cf5ac8f3c5b

.flowconfig

@@ -13,7 +13,6 @@
 
 ; Ignore unexpected extra "@providesModule"
 .*/node_modules/.*/node_modules/fbjs/.*
-+.*/node_modules/react-dom/.*
 
 ; Ignore duplicate module providers
 ; For RN Apps installed via npm, "Libraries" folder is inside