chore: Fix spelling

Merge https://github.com/google/adk-python/pull/2447

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

The misspellings have been reported at https://github.com/jsoref/adk-python/actions/runs/16840838898/attempts/1#summary-47711379253

The action reports that the changes in this PR would make it happy: https://github.com/jsoref/adk-python/actions/runs/16840839269/attempts/1#summary-47711380479

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.

I've included a couple of changes to make CI happy. Personally, I object to CI being in a state of "random drive by person who adds a blank line in the middle of a file must fix all the preexisting bugs in the file", but that appears to be the state for this repository.

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/2447 from jsoref:spelling d85398e7fd154d124d477c6af6181481a01f34e0
PiperOrigin-RevId: 827629615

tests/unittests/tools/test_url_context_tool.py

@@ -146,7 +146,7 @@ class TestUrlContextTool:
     )
 
     with pytest.raises(
-        ValueError, match='Url context tool can not be used in Gemini 1.x'
+        ValueError, match='Url context tool cannot be used in Gemini 1.x'
     ):
       await tool.process_llm_request(
           tool_context=tool_context, llm_request=llm_request
@@ -166,7 +166,7 @@ class TestUrlContextTool:
     )
 
     with pytest.raises(
-        ValueError, match='Url context tool can not be used in Gemini 1.x'
+        ValueError, match='Url context tool cannot be used in Gemini 1.x'
     ):
       await tool.process_llm_request(
           tool_context=tool_context, llm_request=llm_request