Add provider field to agent update functionality

Extended the update_agent method to include the updated_provider parameter in both the REST API connector and agents class. Updated an example script to demonstrate the use of the new provider field for creating and managing agents.

mindsdb_sdk/agents.py

@@ -514,6 +514,7 @@ def update(self, name: str, updated_agent: Agent):
             self.project.name,
             name,
             updated_agent.name,
+            updated_agent.provider,
             updated_agent.model_name,
             list(skills_to_add),
             list(skills_to_remove),

mindsdb_sdk/connectors/rest_api.py

@@ -309,6 +309,7 @@ def update_agent(
             project: str,
             name: str,
             updated_name: str,
+            updated_provider: str,
             updated_model: str,
             skills_to_add: List[str],
             skills_to_remove: List[str],
@@ -321,6 +322,7 @@ def update_agent(
                 'agent': {
                     'name': updated_name,
                     'model_name': updated_model,
+                    'provider': updated_provider,
                     'skills_to_add': skills_to_add,
                     'skills_to_remove': skills_to_remove,
                     'params': updated_params