[TIR] [Docs] Fix unsafe_set_dtype docstring (apache#14611)

Looks like the `unsafe_set_dtype` docs  were not updated after the API was renamed during PR reviews, just fixing that.

python/tvm/tir/schedule/schedule.py

@@ -2581,7 +2581,7 @@ def unsafe_set_dtype(self, block: Union[BlockRV, str], buffer_index: int, dtype:
         Examples
         --------
 
-        Before set_dtype, in TensorIR, the IR is:
+        Before unsafe_set_dtype, in TensorIR, the IR is:
 
         .. code-block:: python
 
@@ -2600,12 +2600,12 @@ def before_set_dtype(
                         vi, vj = T.axis.remap("SS", [i, j]
                         C[vi, vj] = B[vi, vj] + 1.0
 
-        Create the schedule and do set_dtype:
+        Create the schedule and do unsafe_set_dtype:
 
         .. code-block:: python
 
             sch = tir.Schedule(before_set_dtype)
-            sch.set_dtype("B", buffer_index=0, dtype="float16")
+            sch.unsafe_set_dtype("B", buffer_index=0, dtype="float16")
             print(sch.mod["main"].script())
 
         After applying set_dtype, the IR becomes:
@@ -2629,7 +2629,8 @@ def after_set_dtype(
 
         Note
         ----
-        `set_dtype` requires the buffer to be an intermediate buffer defined via `alloc_buffer`.
+        `unsafe_set_dtype` requires the buffer to be an intermediate buffer defined via
+        `alloc_buffer`.
         """
         block = self._normalize_block_arg(block)
         _ffi_api.ScheduleUnsafeSetDType(  # type: ignore # pylint: disable=no-member