Revert "Cygwin: pty: Fix 'Bad address' error when running 'cmd.exe /c dir'"

This reverts commit 7589034cc3.

The previous commit 14816de9af69 ("Cygwin: spawn: drop special handling
for cmd.exe and command.com") make this patch unnecessary.  The filename
argument (i. e., run_path in the caller) is now always non-NULL.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/spawn.cc

@@ -215,8 +215,6 @@ handle (int fd, bool writing)
 static bool
 is_console_app (WCHAR *filename)
 {
-  if (filename == NULL)
-    return true; /* The command executed is command.com or cmd.exe. */
   HANDLE h;
   const int id_offset = 92;
   h = CreateFileW (filename, GENERIC_READ, FILE_SHARE_READ,