Refactor RunnableExecutor.py to add default values for input_key and output_key

src/backend/base/langflow/components/experimental/RunnableExecutor.py

@@ -32,9 +32,9 @@ class RunnableExecComponent(CustomComponent):
 
     def build(
         self,
-        input_key: str,
         input_value: Text,
         runnable: Runnable,
+        input_key: str = "input",
         output_key: str = "output",
     ) -> Text:
         result = runnable.invoke({input_key: input_value})