patch 8.1.0983: checking __CYGWIN32__ unnecessarily

Problem:    Checking __CYGWIN32__ unnecessarily.
Solution:   Remove the checks. (Ken Takata)
diff --git a/src/os_win32.c b/src/os_win32.c
index b923315..4ac5ebd 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -2094,8 +2094,8 @@
     return TRUE;
 }
 
-#if ((defined(__MINGW32__) || defined (__CYGWIN32__)) && \
-       __MSVCRT_VERSION__ >= 0x800) || (defined(_MSC_VER) && _MSC_VER >= 1400)
+#if (defined(__MINGW32__) && __MSVCRT_VERSION__ >= 0x800) || \
+	(defined(_MSC_VER) && _MSC_VER >= 1400)
 /*
  * Bad parameter handler.
  *