fix bug in optimizer-api.md

[zhaoyang-0204]

Fix a small bug in the file 1009-optimizer-api.md, where the new variables after updating should be the dict including new_params, not params.

Fixes # (issue)

Checklist

• This PR fixes a minor issue (e.g.: typo or small bug) or improves the docs (you can dismiss the other
  checks if that's the case).
• This change is discussed in a Github issue/
  discussion (please add a
  link).
• The documentation and docstrings adhere to the
  documentation guidelines.
• This change includes necessary high-coverage tests.
  (No quality testing = no merge!)

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (055e28f) 83.56% compared to head (56fbfb2) 83.56%.
Report is 47 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3462   +/-   ##
=======================================
  Coverage   83.56%   83.56%           
=======================================
  Files          56       56           
  Lines        6768     6768           
=======================================
  Hits         5656     5656           
  Misses       1112     1112           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[chiamp]

Thanks!