Fix issue with incorrect param devs default value

[k-doering-NOAA]

Thanks @charliehinchliffe for pointing out this issue and coming up with the fix! Fixes #186

• Change the default value for param devs to be 1 instead of 0.5.
• Made a note about the default value of rho, which is not used unless implementing a random walk directly in SS3 (we don't do this in SSMSE, so it remains unused).

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 69.83%. Comparing base (ef2b462) to head (3fdef58).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #187 +/- ## ======================================= Coverage 69.83% 69.83% ======================================= Files 21 21 Lines 4396 4396 ======================================= Hits 3070 3070 Misses 1326 1326 ```

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