chore: Fix spelling in src

Merge https://github.com/google/adk-python/pull/3382

This PR corrects misspellings identified by the [check-spelling action](https://github.com/marketplace/actions/check-spelling)

Note: while I use tooling to identify errors, the tooling doesn't _actually_ provide the corrections, I'm picking them on my own. I'm a human, and I may make mistakes.

### Testing Plan

The misspellings have been reported at https://github.com/jsoref/adk-python/actions/runs/19056081305/attempts/1#summary-54426435973

The action reports that the changes in this PR would make it happy: https://github.com/jsoref/adk-python/actions/runs/19056081446/attempts/1#summary-54426436321

**Unit Tests:**

- [ ] I have added or updated unit tests for my change.
- [ ] All unit tests pass locally.

_Please include a summary of passed `pytest` results._

**Manual End-to-End (E2E) Tests:**

_Please provide instructions on how to manually test your changes, including any
necessary setup or configuration. Please provide logs or screenshots to help
reviewers better understand the fix._

### 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.
- [ ] I have commented my code, particularly in hard-to-understand areas.
- [ ] I have added tests that prove my fix is effective or that my feature works.
- [ ] New and existing unit tests pass locally with my changes.
- [ ] I have manually tested my changes end-to-end.
- [ ] Any dependent changes have been merged and published in downstream modules.

### Additional context

- follow-up to #2447

Co-authored-by: Hangfei Lin <hangfei@google.com>
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/3382 from jsoref:spelling 3df5932e97391c437e1638d7163e5e3d5c52d5c3
PiperOrigin-RevId: 828686941

src/google/adk/models/llm_response.py

@@ -33,7 +33,7 @@ class LlmResponse(BaseModel):
   Attributes:
     content: The content of the response.
     grounding_metadata: The grounding metadata of the response.
-    partial: Indicates whether the text content is part of a unfinished text
+    partial: Indicates whether the text content is part of an unfinished text
       stream. Only used for streaming mode and when the content is plain text.
     turn_complete: Indicates whether the response from the model is complete.
       Only used for streaming mode.
@@ -69,7 +69,7 @@ class LlmResponse(BaseModel):
   """The grounding metadata of the response."""
 
   partial: Optional[bool] = None
-  """Indicates whether the text content is part of a unfinished text stream.
+  """Indicates whether the text content is part of an unfinished text stream.
 
   Only used for streaming mode and when the content is plain text.
   """