docs: fixing multiple typos

Merge https://github.com/google/adk-python/pull/4221

### Link to Issue or Description of Change

N/A

**2. Or, if no issue exists, describe the change:**

Fixing various typos in .py files to improve quality: see commit diffs for details

**Problem:**

See above

**Solution:**
Fixing the typos

### Testing Plan

N/A

**Unit Tests:**

N/A

**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.
- [N/A] 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/4221 from didier-durand:fix-typos-e 1bcc8e05cdc116451222dd7fd7b0657745f769c1
PiperOrigin-RevId: 859332402

src/google/adk/cli/adk_web_server.py

@@ -395,7 +395,7 @@ def _setup_gcp_telemetry(
           # TODO - use trace_to_cloud here as well once otel_to_cloud is no
           # longer experimental.
           enable_cloud_tracing=True,
-          # TODO - reenable metrics once errors during shutdown are fixed.
+          # TODO - re-enable metrics once errors during shutdown are fixed.
           enable_cloud_metrics=False,
           enable_cloud_logging=True,
           google_auth=(credentials, project_id),

src/google/adk/cli/cli_tools_click.py

@@ -1299,7 +1299,7 @@ def cli_web(
 ):
   """Starts a FastAPI server with Web UI for agents.
 
-  AGENTS_DIR: The directory of agents, where each sub-directory is a single
+  AGENTS_DIR: The directory of agents, where each subdirectory is a single
   agent, containing at least `__init__.py` and `agent.py` files.
 
   Example:
@@ -1366,7 +1366,7 @@ def cli_web(
 
 @main.command("api_server")
 @feature_options()
-# The directory of agents, where each sub-directory is a single agent.
+# The directory of agents, where each subdirectory is a single agent.
 # By default, it is the current working directory
 @click.argument(
     "agents_dir",
@@ -1401,7 +1401,7 @@ def cli_api_server(
 ):
   """Starts a FastAPI server for agents.
 
-  AGENTS_DIR: The directory of agents, where each sub-directory is a single
+  AGENTS_DIR: The directory of agents, where each subdirectory is a single
   agent, containing at least `__init__.py` and `agent.py` files.
 
   Example: