Fix duplicate function declaration in WebSockets (#22098)

Summary:
Fixes the only ESLint error pending to resolve. It was a duplicate `get` declaration.
Pull Request resolved: https://github.com/facebook/react-native/pull/22098

Differential Revision: D12918078

Pulled By: TheSavior

fbshipit-source-id: c738d6880241dbc1f1ddc06c2d4e52443c00768a

Libraries/WebSocket/WebSocket.js

@@ -175,10 +175,6 @@ class WebSocket extends EventTarget(...WEBSOCKET_EVENTS) {
     this._binaryType = binaryType;
   }
 
-  get binaryType(): ?BinaryType {
-    return this._binaryType;
-  }
-
   close(code?: number, reason?: string): void {
     if (this.readyState === this.CLOSING || this.readyState === this.CLOSED) {
       return;