ai-endpoints[patch]: permit 'Bad Request' error message in integration tests

[ccurme]

In addition to error codes, integration tests check for expected strings in the error message. These checks have been failing for the past three days. Here we update the checks to accommodate the new language.

Some alternatives:

• Relax these tests and just check the error code;
• Add logic inside the library to catch the errors and raise a desired error message.

[ccurme]

Integration tests pass: https://github.com/langchain-ai/langchain-nvidia/actions/runs/10509258297

[mattf]

@ccurme thank you for keeping an eye out. this is caused by a regression on the server side. give me a few days to see if i can get it resolved.

[mattf]

@ccurme thank you for watching this. the server side has been fixed and i'm going to keep the tests as a check against server side changes.