fix: Fix typo in several files

Merge https://github.com/google/adk-python/pull/3365

**Please ensure you have read the [contribution guide](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) before creating a pull request.**

fix typo for several files.

### 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.
- [x] New and existing unit tests pass locally with my changes.
- [x] I have manually tested my changes end-to-end.
- [x] Any dependent changes have been merged and published in downstream modules.

### Additional context

_Add any other context or screenshots about the feature request here._

Co-authored-by: Liang Wu <wuliang@google.com>
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/3365 from UlookEE:fix_typo 1469de4ea354d1c205268b999183ee86c9d6a1d5
PiperOrigin-RevId: 827724001

src/google/adk/agents/parallel_agent.py

@@ -160,7 +160,7 @@ async def _merge_agent_run(
 
 
 class ParallelAgent(BaseAgent):
-  """A shell agent that run its sub-agents in parallel in isolated manner.
+  """A shell agent that runs its sub-agents in parallel in an isolated manner.
 
   This approach is beneficial for scenarios requiring multiple perspectives or
   attempts on a single task, such as:

src/google/adk/evaluation/base_eval_service.py

@@ -31,7 +31,7 @@ from .eval_result import EvalCaseResult
 
 
 class EvaluateConfig(BaseModel):
-  """Contains configurations need to run an evaluations."""
+  """Contains configurations needed to run evaluations."""
 
   model_config = ConfigDict(
       alias_generator=alias_generators.to_camel,

src/google/adk/evaluation/eval_sets_manager.py

@@ -23,7 +23,7 @@ from .eval_set import EvalSet
 
 
 class EvalSetsManager(ABC):
-  """An interface to manage an Eval Sets."""
+  """An interface to manage Eval Sets."""
 
   @abstractmethod
   def get_eval_set(self, app_name: str, eval_set_id: str) -> Optional[EvalSet]:

src/google/adk/flows/llm_flows/functions.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Handles function callings for LLM flow."""
+"""Handles function calling for LLM flow."""
 
 from __future__ import annotations
 

src/google/adk/sessions/state.py

@@ -12,11 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
 from typing import Any
 
 
 class State:
-  """A state dict that maintain the current value and the pending-commit delta."""
+  """A state dict that maintains the current value and the pending-commit delta."""
 
   APP_PREFIX = "app:"
   USER_PREFIX = "user:"

src/google/adk/telemetry/tracing.py

@@ -86,7 +86,7 @@ def _safe_json_serialize(obj) -> str:
 def trace_agent_invocation(
     span: trace.Span, agent: BaseAgent, ctx: InvocationContext
 ) -> None:
-  """Sets span attributes immedietely available on agent invocation according to OTEL semconv version 1.37.
+  """Sets span attributes immediately available on agent invocation according to OTEL semconv version 1.37.
 
   Args:
     span: Span on which attributes are set.