📝 Description

Related Issue: #160

💡 Summary of Changes

Split the error of ""The parameters 'model', 'model_id' and 'deployment_id' are "
"mutually exclusive. Please specify exactly one of these "
"parameters when initializing ChatWatsonx."

To 2 cases to be more descriptive, one when there is no parameter passed and a second when there is more than one passed.

✅ PR Checklist

• PR Title Format: {TYPE}({SCOPE}): {DESCRIPTION}

  • Examples:
    • feat(langchain-ibm): add multi-tenant support
    • fix(langchain-db2): resolve flag parsing error
    • docs(langchain-ibm): update API usage examples
  • Allowed {TYPE} values:
    feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert, release
  • Allowed {SCOPE} values (optional):
    langchain-ibm, langchain-db2

• PR Description: The Description section clearly lists what was changed, why, and how it was tested.

• Formatting, Linting & Tests
  Run the following commands from the root of the modified package(s):

  make format
  make lint
  make test

  ⚠️ PRs will only be considered if all checks pass in CI.
  See the contribution guidelines for more details.

🧪 Testing (optional)

🗒️ Notes (optional)

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