bpo-35233: Fix test_embed.InitConfigTests on macOS (GH-10539)

On macOS and Windows, Py_HasFileSystemDefaultEncoding is 1 by
default.
diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index 856116f..6e2e212 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -287,9 +287,10 @@
         'Py_VerboseFlag': 0,
     }
     if os.name == 'nt':
-        DEFAULT_GLOBAL_CONFIG['Py_HasFileSystemDefaultEncoding'] = 1
         DEFAULT_GLOBAL_CONFIG['Py_LegacyWindowsFSEncodingFlag'] = 0
         DEFAULT_GLOBAL_CONFIG['Py_LegacyWindowsStdioFlag'] = 0
+    if sys.platform in ('win32', 'darwin'):
+        DEFAULT_GLOBAL_CONFIG['Py_HasFileSystemDefaultEncoding'] = 1
 
     DEFAULT_CORE_CONFIG = {
         'install_signal_handlers': 1,