Fix: Change model_type from ssm to mamba (#2740)

Co-authored-by: Ubuntu <ubuntu@ip-172-31-28-135.us-west-2.compute.internal>

server/text_generation_server/models/__init__.py

@@ -534,7 +534,7 @@ def get_model(
         # TODO: fix how we determine model type for Mamba
         if "ssm_cfg" in config_dict:
             # *only happens in Mamba case
-            model_type = "ssm"
+            model_type = "mamba"
         else:
             raise RuntimeError(
                 f"Could not determine model type for {model_id} revision {revision}"