Update _core.py with multiline exception message

pandas/plotting/_core.py

@@ -961,7 +961,10 @@ def __call__(self, *args, **kwargs):
             return plot_backend.plot(self._parent, x=x, y=y, kind=kind, **kwargs)
 
         if kind not in self._all_kinds:
-            raise ValueError(f"{kind} is not a valid plot kind\nValid plot kinds {self._all_kinds}")
+            raise ValueError(
+                    f"{kind} is not a valid plot kind "
+                    f"Valid plot kinds: {self._all_kinds}"
+                )
 
         # The original data structured can be transformed before passed to the
         # backend. For example, for DataFrame is common to set the index as the