rsaenh/tests: Adjust length value to pass on Win 10

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=16775

Your paranoid android.


=== w1064 (32 bit rsaenh) ===
rsaenh.c:2804: Test failed: 80090020

=== w1064 (64 bit rsaenh) ===
rsaenh.c:2804: Test failed: 80090020