[Bug]: mirroring was not working for age discard

[Rick-Methot-NOAA]

Describe the bug

mirroring age retention parameters was producing incorrect results. Rick goes under the hood and finds flawed logic. Seems that this feature has never been tried or tested.

To Reproduce

set do_checkup to 1 and look in echoinput for fleet_specific output of sel_ret_bio

Expected behavior

retention vectors get mirrored as requested

Screenshots

No response

Which OS are you seeing the problem on?

Windows

Which version of SS3 are you seeing the problem on?

No response

Additional Context

No response