!12704 fix the format error of MatrixSetDiag operator.

From: @wangshuide2020
Reviewed-by: @liangchenghui,@ljl0711
Signed-off-by: @liangchenghui

mindspore/nn/layer/basic.py

@@ -1008,9 +1008,11 @@ class MatrixSetDiag(Cell):
     dimensions :math:`[I, J, K, ..., min(M, N)]`. Then the output is a tensor of rank :math:`k+1` with dimensions
     :math:`[I, J, K, ..., M, N]` where:
 
-    :math:`output[i, j, k, ..., m, n] = diagnoal[i, j, k, ..., n]\ for\ m == n`
+    .. math::
+        output[i, j, k, ..., m, n] = diagnoal[i, j, k, ..., n]\ for\ m == n
 
-    :math:`output[i, j, k, ..., m, n] = x[i, j, k, ..., m, n]\ for\ m != n`
+    .. math::
+        output[i, j, k, ..., m, n] = x[i, j, k, ..., m, n]\ for\ m != n
 
     Inputs:
         - **x** (Tensor) - The batched tensor. Rank k+1, where k >= 1. It can be one of the following data types: