PyUnicode_DecodeFSDefaultAndSize() uses surrogateescape error handler

This function is only used to decode Python module filenames, but Python
doesn't support surrogates in modules filenames yet. So nobody noticed this
minor bug.
diff --git a/Misc/NEWS b/Misc/NEWS
index e1b0116..b7e9318 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
 Core and Builtins
 -----------------
 
+- PyUnicode_DecodeFSDefaultAndSize() uses surrogateescape error handler
+
 - Issue #8419: Prevent the dict constructor from accepting non-string keyword
   arguments.