fix: Correct various typos in CHANGELOG.md and test_rest_api_tool.py

Corrected the following spelling errors:
 - CHANGELOG.md: "impprovements" -> "improvements"
 - test_rest_api_tool.py: "def sample_endpiont:" -> "def sample_endpoint:"
 - CHANGELOG.md: "credentails" -> "credentials"
 - CHANGELOG.md: "auido" -> "audio"

Author: knileshh

CHANGELOG.md

@@ -5,7 +5,7 @@
 ### ⚠ BREAKING CHANGES
 
 * Auth: expose `access_token` and `refresh_token` at top level of auth
-  credentails, instead of a `dict`
+  credentials, instead of a `dict`
   ([commit](https://github.com/google/adk-python/commit/956fb912e8851b139668b1ccb8db10fd252a6990)).
 
 ### Features
@@ -28,7 +28,7 @@
 
 ### Miscellaneous Chores
 
-* README.md impprovements.
+* README.md improvements.
 * Various code improvements.
 * Various typo fixes.
 * Bump min version of google-genai to 1.11.0.
@@ -86,4 +86,4 @@
 * Built-in evaluation support
 * Development UI that makes local development easy
 * Deploy to Google Cloud Run, Agent Engine
-* (Experimental) Live(Bidi) auido/video agent support and Compositional Function Calling(CFC) support
+* (Experimental) Live(Bidi) audio/video agent support and Compositional Function Calling(CFC) support

tests/unittests/tools/openapi_tool/openapi_spec_parser/test_rest_api_tool.py

@@ -61,7 +61,7 @@ def mock_operation_parser(self):
     return mock_parser
 
   @pytest.fixture
-  def sample_endpiont(self):
+  def sample_endpoint(self):
     return OperationEndpoint(
         base_url="https://example.com", path="/test", method="GET"
     )