fix: use correct way of getting tmb output

[k-doering-NOAA]

What is the feature?

• Small change to correct how to get TMB output - thanks @Andrea-Havron-NOAA for identifying in [Bug]: Difference in point estimates from tmb sdreport vs. tmb output object #616

How have you implemented the solution?

Modified one line for the tmb output

Does the PR impact any other area of the project?

case studies should also be modified

How to test this change

I think this has already been tested by @Bai-Li-NOAA, as discussed in #616

Developer pre-PR checklist

• I relied on GitHub actions to 🧪 things for me while I sat on the 🛋️.

[github-actions]

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Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.56%. Comparing base (e12e353) to head (4a03ce9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #620   +/-   ##
=======================================
  Coverage   78.56%   78.56%           
=======================================
  Files          36       36           
  Lines        1945     1945           
  Branches      141      141           
=======================================
  Hits         1528     1528           
  Misses        374      374           
  Partials       43       43           

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