fixed misspells

[leo-gan]

Sorry for this PR. I don't like this kind of fix. But some misspellings are in prompts and docstrings, hence could confuse LLMs. I started, then decided to do it on several more files. Feel free to Close it, if it's not necessary.

[google-cla[bot]]

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.