Remove unused variables (#22097)

Summary:
Fix unused variable ESLint warnings.
Pull Request resolved: https://github.com/facebook/react-native/pull/22097

Differential Revision: D12919249

Pulled By: TheSavior

fbshipit-source-id: f680fa7277c58cf685e70dfb911753a30fe01c1d

Libraries/Core/Devtools/setupDevtools.js

@@ -10,16 +10,6 @@
 
 'use strict';
 
-type DevToolsPluginConnection = {
-  isAppActive: () => boolean,
-  host: string,
-  port: number,
-};
-
-type DevToolsPlugin = {
-  connectToDevTools: (connection: DevToolsPluginConnection) => void,
-};
-
 let register = function() {
   // noop
 };