remove support for BSD/OS (closes bpo-31624) (#3812)

diff --git a/Lib/test/test_fcntl.py b/Lib/test/test_fcntl.py
index e3b7ed2..acd5c7c 100644
--- a/Lib/test/test_fcntl.py
+++ b/Lib/test/test_fcntl.py
@@ -22,7 +22,7 @@
     else:
         start_len = "qq"
 
-    if (sys.platform.startswith(('netbsd', 'freebsd', 'openbsd', 'bsdos'))
+    if (sys.platform.startswith(('netbsd', 'freebsd', 'openbsd'))
         or sys.platform == 'darwin'):
         if struct.calcsize('l') == 8:
             off_t = 'l'