Revert "improved typing of FlowLink"

This reverts commit 37d1b26.

rasa/shared/core/flows/flow.py

@@ -1130,12 +1130,17 @@ def as_json(self) -> Any:
         return [link.as_json() for link in self.links]
 
 
-@dataclass
-class FlowLink:
+class FlowLink(Protocol):
     """Represents a flow link."""
 
-    target: str
-    """The id of the linked flow."""
+    @property
+    def target(self) -> Text:
+        """Returns the target of the flow link.
+
+        Returns:
+            The target of the flow link.
+        """
+        ...
 
     def as_json(self) -> Any:
         """Returns the flow link as a dictionary.
@@ -1159,9 +1164,11 @@ def from_json(link_config: Any) -> FlowLink:
 
 
 @dataclass
-class IfFlowLink(FlowLink):
+class IfFlowLink:
     """Represents the configuration of an if flow link."""
 
+    target: Text
+    """The id of the linked flow."""
     condition: Optional[Text]
     """The condition of the linked flow."""
 
@@ -1190,9 +1197,12 @@ def as_json(self) -> Dict[Text, Any]:
 
 
 @dataclass
-class ElseFlowLink(FlowLink):
+class ElseFlowLink:
     """Represents the configuration of an else flow link."""
 
+    target: Text
+    """The id of the linked flow."""
+
     @staticmethod
     def from_json(link_config: Dict[Text, Any]) -> ElseFlowLink:
         """Used to read flow links from parsed YAML.
@@ -1215,9 +1225,12 @@ def as_json(self) -> Dict[Text, Any]:
 
 
 @dataclass
-class StaticFlowLink(FlowLink):
+class StaticFlowLink:
     """Represents the configuration of a static flow link."""
 
+    target: Text
+    """The id of the linked flow."""
+
     @staticmethod
     def from_json(link_config: Text) -> StaticFlowLink:
         """Used to read flow links from parsed YAML.