Merge https://github.com/google/adk-python/pull/3944
### Link to Issue or Description of Change
**1. Link to an existing issue (if applicable):** N/A
**2. Or, if no issue exists, describe the change:** fixing various typos in multiple files: see commit diffs for details
**Problem:**
Discovered typos while reading ADK repo
**Solution:**
Submitted this PR to fix them
### Testing Plan
N/A: changes only in comments, .md and docstrings.
**Unit Tests:**
- [N/A ] I have added or updated unit tests for my change.
- [X] All unit tests pass locally.
_Please include a summary of passed `pytest` results._
**Manual End-to-End (E2E) Tests:**
N/A
### Checklist
- [X] I have read the [CONTRIBUTING.md](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) document.
- [X] I have performed a self-review of my own code.
- [N/A] I have commented my code, particularly in hard-to-understand areas.
- [N/A] I have added tests that prove my fix is effective or that my feature works.
- [X] New and existing unit tests pass locally with my changes.
- [N/A] I have manually tested my changes end-to-end.
- [N/A] Any dependent changes have been merged and published in downstream modules.
### Additional context
N/A
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/3944 from didier-durand:fix-typos-a 02378a488d9a87ac9b6b7397fe9ad7c393faf16a
PiperOrigin-RevId: 868245940
Didier Durand
80ff067c6b