message: Fix formatting of mlir snippet.
diff: @@ -141,18 +141,28 @@ unknown dimension can be queried using the "dim" builtin as shown below.
  Example:
  ``` {.mlir}
  -mlfunc foo(...) { %A = alloc <8x?xf32, #lmap> (%N) ... call bar(%A) :
  -(memref<8x?xf32, #lmap>) }
  +mlfunc foo(...) {
  + %A = alloc <8x?xf32, #lmap> (%N)
  + ...
  + call bar(%A) : (memref<8x?xf32, #lmap>)
  +}
  mlfunc bar(%A : memref<8x?xf32, #lmap>) {
  -
  -// Type of %A indicates that %A has dynamic shape with 8 rows // and unknown
  -number of columns. The number of columns is queried // dynamically using dim
  -instruction. %N = builtin "dim"(%A){index : 1} : (memref<8x?xf32, #lmap>) -> int
  -
  -for %i = 0 to 15 { for %j = 0 to %N { // A[i,j] += 1 %s1 = load %A [%i, %j] :
  -memref<8x?xf32, #lmap> %s2 = add %s1, 1 store %s2 to %A [%i, %j] :
  -memref<8x?xf32, #lmap> } } return }
  + // Type of %A indicates that %A has dynamic shape with 8 rows
  + // and unknown number of columns. The number of columns is queried
  + // dynamically using dim instruction.
  + %N = builtin "dim"(%A){index : 1} : (memref<8x?xf32, #lmap>) -> int
  +
  + for %i = 0 to 15 {
  + for %j = 0 to %N {
  + // A[i,j] += 1
  + %s1 = load %A [%i, %j] : memref<8x?xf32, #lmap>
  + %s2 = add %s1, 1
  + store %s2 to %A [%i, %j] : memref<8x?xf32, #lmap>
  + }
  + }
  + return
  +}
  ```
  