Update historic period end (and projection period start) from 2018 assessment to 2023 assessment

[kristinmarshall-NOAA]

Sandra is working on updating the operating model so that the historic period runs through the most recent stock assessment year, and the projections would start the following year. The current version uses the 2018 stock assessment.

@kellijohnson-NOAA or @cgrandin Could you help Sandra locate the SS files she needs from last year's assessment? Thank you!