Add missing f str (#306)

Co-authored-by: Chunyang Wen <[email protected]>

python/mlx/nn/layers/dropout.py

@@ -19,7 +19,7 @@ class Dropout(Module):
         super().__init__()
 
         if p < 0 or p >= 1:
-            raise ValueError("The dropout probability {p} is not in [0, 1)")
+            raise ValueError(f"The dropout probability {p} is not in [0, 1)")
 
         self._p_1 = 1 - p