Replace $ObjMap in EventEmitter with mapped type (#46332)

Summary:
Pull Request resolved: #46332

Changelog: [Internal]

Reviewed By: gkz

Differential Revision: D62199703

fbshipit-source-id: 24abf39b01d5ba8a90e03ce837a887d4b4f4ade8

packages/react-native/Libraries/vendor/emitter/EventEmitter.js

@@ -35,11 +35,9 @@ interface Registration<TArgs> {
   +remove: () => void;
 }
 
-// $FlowFixMe[deprecated-type]
-type Registry<TEventToArgsMap: {...}> = $ObjMap<
-  TEventToArgsMap,
-  <TArgs>(TArgs) => Set<Registration<TArgs>>,
->;
+type Registry<TEventToArgsMap: {...}> = {
+  [K in keyof TEventToArgsMap]: Set<Registration<TEventToArgsMap[K]>>,
+};
 
 /**
  * EventEmitter manages listeners and publishes events to them.
@@ -64,6 +62,7 @@ type Registry<TEventToArgsMap: {...}> = $ObjMap<
 export default class EventEmitter<TEventToArgsMap: {...}>
   implements IEventEmitter<TEventToArgsMap>
 {
+  // $FlowFixMe[incompatible-type]
   #registry: Registry<TEventToArgsMap> = {};
 
   /**
@@ -126,6 +125,7 @@ export default class EventEmitter<TEventToArgsMap: {...}>
     eventType?: ?TEvent,
   ): void {
     if (eventType == null) {
+      // $FlowFixMe[incompatible-type]
       this.#registry = {};
     } else {
       delete this.#registry[eventType];