Fix typo in RCTConvert.m (#31067)

Summary:
seperated -> separated

## Changelog

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[Internal] [Fixed] - Fixed typo in comment

Pull Request resolved: #31067

Test Plan: NONE

Reviewed By: sammy-SC

Differential Revision: D30176244

Pulled By: sota000

fbshipit-source-id: 617607aaa7eb5f613344773c4bbbc09a8c5096c1

React/Base/RCTConvert.m

@@ -807,7 +807,7 @@ +(type)type : (id)json                                      \
   return color;
 }
 
-/** Returns an alphabetically sorted comma seperated list of the valid semantic color names
+/** Returns an alphabetically sorted comma separated list of the valid semantic color names
  */
 static NSString *RCTSemanticColorNames()
 {