add float16 to index_sample eng doc (#49317)

python/paddle/tensor/search.py

@@ -734,7 +734,7 @@ def index_sample(x, index):
 
     Args:
         x (Tensor): The source input tensor with 2-D shape. Supported data type is
-            int32, int64, float32, float64.
+            int32, int64, float16, float32, float64.
         index (Tensor): The index input tensor with 2-D shape, first dimension should be same with X.
             Data type is int32 or int64.