[Bug]: proportion female at age

[KyleShertzer-NOAA]

Describe the bug

A vector of sex ratio at age appears to be accepted as FIMS input, using "population$proportion_female <- vector" However, this capability is not currently implemented, with sex ratio hard coded at 0.5.

To Reproduce

No response

Screenshots

No response

Which OS are you seeing the problem on?

Windows

Which browser are you seeing the problem on?

Other

Which version of FIMS are you seeing the problem on?

FIMS_0.2.0.0

Additional Context

For the southeast scamp example, I want to specify the sex ratio at age as 100% female. This is a work-around to mimic how BAM handles SSB of a protogynous hermaphrodite, as total (male + female) mature biomass. Current FIMS assumes sex ratio is 50:50, which means that in the scamp example, FIMS-predicted SSB is half that of BAM-predicted SSB.

### Tasks
- [x] Remove it from the user interface
- [ ] Ensure that it is hard coded at the value we want 0.5
- [x] Remove proportion_female from vignette - it was not in the vignette
- [x] Remove proportion_female from case studies
- [ ] Make sure there is documentation on the sb calculation that it uses 0.5
- [ ] Start a design document about what proportion_female means and how it should be modeled or input

[kellijohnson-NOAA]

This older PR is relevant. @Bai-Li-NOAA will work with the "fixer" of this bug to help design tests.

Thoughts for fixing ... "prepare" function in population where a lot of values are set and it is possible that it is being reset in the prepare function.

[kellijohnson-NOAA]

Thank you @KyleShertzer-NOAA for bringing this up. During NOAA-FIMS/seasid-chats#7 we decided to remove the capability of the user to set this because it is not currently doing anything and then later in the future we can revisit what proportion_female should be doing. There is now a task list at the top of this issue for how to fix it.