chore: correct typo in pyproject.toml (swtich → switch)

Merge #2651

### Summary
Correct a misspelling in the build configuration:
- "swtich" → "switch" in `pyproject.toml`.

### Rationale
This is a spelling fix only. It improves readability and avoids potential confusion in configuration.
There is no impact on runtime behavior, tests, or public APIs.

### Notes
- Follows Conventional Commits style for build/config changes (`build:`).
- CLA status should be green via the Google CLA bot.

COPYBARA_INTEGRATE_REVIEW=#2651 from marsboy02:docs/fix-type-pyproject b78c014
PiperOrigin-RevId: 828221776

Author: marsboy02

pyproject.toml

@@ -206,7 +206,7 @@ asyncio_mode = "auto"
 python_version = "3.9"
 exclude = "tests/"
 plugins = ["pydantic.mypy"]
-# Start with non-strict mode, and swtich to strict mode later.
+# Start with non-strict mode, and switch to strict mode later.
 # strict = true
 disable_error_code = ["import-not-found", "import-untyped", "unused-ignore"]
 follow_imports = "skip"