Revert "chore: don't set the new architecture by default for macOS yet (microsoft#2423)"

This reverts commit f2a6793.

Author: Saadnajmi

packages/react-native/scripts/cocoapods/__tests__/new_architecture-test.rb

@@ -249,10 +249,10 @@ def test_newArchEnabled_whenRCTNewArchEnabledIsSetTo0_returnFalse
         assert_false(is_enabled)
     end
 
-    def test_newArchEnabled_whenRCTNewArchEnabledIsNotSet_returnFalse  # [macOS] Disable Fabric by default till macOS supports it]
+    def test_newArchEnabled_whenRCTNewArchEnabledIsNotSet_returnTrue
         ENV["RCT_NEW_ARCH_ENABLED"] = nil
         is_enabled = NewArchitectureHelper.new_arch_enabled
-        assert_false(is_enabled)
+        assert_true(is_enabled)
     end
 
 

packages/react-native/scripts/cocoapods/new_architecture.rb

@@ -157,6 +157,6 @@ def self.extract_react_native_version(react_native_path, file_manager: File, jso
     end
 
     def self.new_arch_enabled
-        return ENV["RCT_NEW_ARCH_ENABLED"] == "1" # [macOS] Disable Fabric by default till macOS supports it
+        return ENV["RCT_NEW_ARCH_ENABLED"] == nil || ENV["RCT_NEW_ARCH_ENABLED"] == "1"
     end
 end