OptFunc docstring minor updates

[Vaibhavdixit02]

Checklist

• [ ] Appropriate tests were added
• [ ] Any code changes were done in a way that does not break public API
• [ ] All documentation related to code changes were updated
• [ ] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [ ] Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[codecov[bot]]

Codecov Report

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

Project coverage is 38.49%. Comparing base (9e29cfa) to head (b714c43).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #650 +/- ## ======================================= Coverage 38.49% 38.49% ======================================= Files 55 55 Lines 4291 4291 ======================================= Hits 1652 1652 Misses 2639 2639 ```

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