Remove pipes from Object literal Flow types

Summary:
## Changes
{| ... |} -> { ... }

**Motivation:** In Flow, object literals are exact by default. So, there's no need for the pipes. Also: Now, the syntax for object literals is consistent across react-native-codegen.

Changelog: [Internal]

Reviewed By: hramos

Differential Revision: D24774771

fbshipit-source-id: 24ceb6f5876122aa8ad9e08c7e903215864ad6f5

packages/react-native-codegen/src/generators/modules/GenerateModuleH.js

@@ -26,7 +26,7 @@ type FilesOutput = Map<string, string>;
 const ModuleClassDeclarationTemplate = ({
   hasteModuleName,
   moduleProperties,
-}: $ReadOnly<{|hasteModuleName: string, moduleProperties: string|}>) => {
+}: $ReadOnly<{hasteModuleName: string, moduleProperties: string}>) => {
   return `class JSI_EXPORT ${hasteModuleName}CxxSpecJSI : public TurboModule {
 protected:
   ${hasteModuleName}CxxSpecJSI(std::shared_ptr<CallInvoker> jsInvoker);
@@ -39,9 +39,9 @@ ${moduleProperties}
 
 const FileTemplate = ({
   modules,
-}: $ReadOnly<{|
+}: $ReadOnly<{
   modules: string,
-|}>) => {
+}>) => {
   return `/**
  * ${'C'}opyright (c) Facebook, Inc. and its affiliates.
  *