bpo-40297: Fix test_socket.CANTest.testSendFrame (GH-19548)

The address tuple for CAN_RAW no longer returns the address family
after the introduction of CAN ISO-TP support in a30f6d45ac. However,
updating test_socket.CANTest.testSendFrame was missed as part of the
change, so the test incorrectly attempts to index past the last tuple
item to retrieve the address family.

This removes the now-redundant check for equality against socket.AF_CAN,
as the tuple will not contain the address family.

Lib/test/test_socket.py

@@ -224,7 +224,7 @@ class SocketCANTest(unittest.TestCase):
     the following commands:
     # modprobe vcan
     # ip link add dev vcan0 type vcan
-    # ifconfig vcan0 up
+    # ip link set up vcan0
     """
     interface = 'vcan0'
     bufsize = 128
@@ -2085,7 +2085,6 @@ def testSendFrame(self):
         cf, addr = self.s.recvfrom(self.bufsize)
         self.assertEqual(self.cf, cf)
         self.assertEqual(addr[0], self.interface)
-        self.assertEqual(addr[1], socket.AF_CAN)
 
     def _testSendFrame(self):
         self.cf = self.build_can_frame(0x00, b'\x01\x02\x03\x04\x05')