Remove extra space in source_files

Summary:
This was causing tvOS builds to fail because .m files weren’t being included.

 - Add `tvOS` subspec to your project with a tvOS target.
 - Build
 - Profit.

[TVOS] [BREAKING] [React.podspec] - Fix building for tvOS with CocoaPods
Closes https://github.com/facebook/react-native/pull/18812

Differential Revision: D7680224

Pulled By: hramos

fbshipit-source-id: c6c3b6fb0acd2004579d85c3f72e4edd88e26ed8

React.podspec

@@ -105,7 +105,7 @@ Pod::Spec.new do |s|
 
   s.subspec "tvOS" do |ss|
     ss.dependency             "React/Core"
-    ss.source_files         = "React/**/RCTTV*.{h, m}"
+    ss.source_files         = "React/**/RCTTV*.{h,m}"
   end
 
   s.subspec "jschelpers" do |ss|