bpo-36503: remove references to 'aix3' and 'aix4' (GH-12658)

diff --git a/Lib/test/test_fcntl.py b/Lib/test/test_fcntl.py
index acd5c7c..5d4abe3 100644
--- a/Lib/test/test_fcntl.py
+++ b/Lib/test/test_fcntl.py
@@ -34,7 +34,7 @@
                                fcntl.F_WRLCK, 0)
     elif sys.platform.startswith('gnukfreebsd'):
         lockdata = struct.pack('qqihhi', 0, 0, 0, fcntl.F_WRLCK, 0, 0)
-    elif sys.platform in ['aix3', 'aix4', 'hp-uxB', 'unixware7']:
+    elif sys.platform in ['hp-uxB', 'unixware7']:
         lockdata = struct.pack('hhlllii', fcntl.F_WRLCK, 0, 0, 0, 0, 0, 0)
     else:
         lockdata = struct.pack('hh'+start_len+'hh', fcntl.F_WRLCK, 0, 0, 0, 0, 0)