Improve azure-ai-evaluation error message

Currently the error message mentions that only `dict` is an acceptable type
for the parameter `azure_ai_project`.
This is incorrect as also a `str` containing a project URI is acceptable.

Author: mzat-msft

sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_common/utils.py

@@ -146,7 +146,7 @@ def validate_azure_ai_project(o: object) -> AzureAIProject:
         return o
 
     if not isinstance(o, dict):
-        msg = "The 'azure_ai_project' parameter must be a dictionary."
+        msg = "The 'azure_ai_project' parameter must be a dictionary or a project URI string."
         raise EvaluationException(
             message=msg,
             category=ErrorCategory.INVALID_VALUE,