Revert "Address CR comment"

This reverts commit 3fcfce9.

Author: kjamrozy

libs/labelbox/src/labelbox/schema/tool_building/tool_type_mapping.py

@@ -6,15 +6,9 @@
     StepReasoningTool,
 )
 from labelbox.schema.tool_building.tool_type import ToolType
-from labelbox.schema.ontology import Tool
-from labelbox.schema.tool_building.relationship_tool import RelationshipTool
 
 
 def map_tool_type_to_tool_cls(tool_type_str: str):
-    # Relationship tool uses a legacy tool type, so we need to handle it separately.
-    if tool_type_str.lower() == Tool.Type.RELATIONSHIP:
-        return RelationshipTool()
-
     if not ToolType.valid(tool_type_str):
         return None