tests/net_inet: Add 'Strict-Transport-Security' to exp file.

Because micropython.org now adds this to the headers.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

tests/net_inet/uasyncio_tcp_read_headers.py.exp

@@ -5,6 +5,7 @@ b'Content-Length: 54'
 b'Connection: close'
 b'Vary: Accept-Encoding'
 b'ETag: "54306c85-36"'
+b'Strict-Transport-Security: max-age=15768000'
 b'Accept-Ranges: bytes'
 close
 done