Use DSI GroupByMetricReference (#1340)

Tiny cleanup. Moved this class to DSI recently, but hadn't gotten around
to removing the MF implementation.

metricflow-semantics/metricflow_semantics/model/semantics/linkable_element.py

@@ -12,7 +12,7 @@
 from dbt_semantic_interfaces.references import (
     DimensionReference,
     EntityReference,
-    LinkableElementReference,
+    GroupByMetricReference,
     MetricReference,
     SemanticModelReference,
 )
@@ -217,17 +217,6 @@ def semantic_model_origin(self) -> SemanticModelReference:
         return self.defined_in_semantic_model
 
 
-# TODO: add to DSI
-@dataclass(frozen=True)
-class GroupByMetricReference(LinkableElementReference):
-    """Represents a group by metric.
-
-    Different from MetricReference because it inherits linkable element attributes.
-    """
-
-    pass
-
-
 @dataclass(frozen=True)
 class LinkableMetric(LinkableElement, SerializableDataclass):
     """Describes how a metric can be realized by joining based on entity links."""

metricflow-semantics/metricflow_semantics/specs/group_by_metric_spec.py

@@ -4,14 +4,10 @@
 from typing import Any, Tuple
 
 from dbt_semantic_interfaces.dataclass_serialization import SerializableDataclass
-from dbt_semantic_interfaces.references import EntityReference
+from dbt_semantic_interfaces.references import EntityReference, GroupByMetricReference
 from typing_extensions import override
 
-from metricflow_semantics.model.semantics.linkable_element import (
-    ElementPathKey,
-    GroupByMetricReference,
-    LinkableElementType,
-)
+from metricflow_semantics.model.semantics.linkable_element import ElementPathKey, LinkableElementType
 from metricflow_semantics.naming.linkable_spec_name import StructuredLinkableSpecName
 from metricflow_semantics.specs.entity_spec import EntitySpec
 from metricflow_semantics.specs.instance_spec import InstanceSpecVisitor, LinkableInstanceSpec