[mlir][memref] Remove extra brackets in doc

[Peiming]

Summary

There is an (probably) unintended bracket in the documentation for memref.subview. See https://mlir.llvm.org/docs/Dialects/MemRef/#memrefsubview-mlirmemrefsubviewop below Example 5.

[aartbik]

I am baffled this worked, but perhaps tablegen is more forgiving than I thought?!

[jpienaar]

Markdown is probably the forgiving one :) tblgen side [{ and }] demark the string literal but beyond that it doesn't care.

But yeah I was looking at some of the ops on mlir.dev and noticed some formatting issues, thanks for fixing this one!

mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td

let description = [{
     // (d0, d1, d2) -> (64 * d0 + 16 * d1 + d2)
     // Subviewed layout:
     // (d0, d1, d2) -> (64 * (d0 + 3) + 4 * (d1 + 4) + d2 + 2) = (64 * d0 + 4 * d1 + d2 + 210)
     // After rank reducing:
     // (d0, d1) -> (4 * d0 + d1 + 210)
     %3 = memref.subview %2[3, 4, 2][1, 6, 3][1, 1, 1] :
       memref<8x16x4xf32> to memref<6x3xf32, offset: 210, strides: [4, 1]>
     ```
-    }
   }];
 
   let arguments = (ins AnyMemRef:$source,
                        Variadic<Index>:$offsets,
                        Variadic<Index>:$sizes,
                        Variadic<Index>:$strides,
                        I64ArrayAttr:$static_offsets,
                        I64ArrayAttr:$static_sizes,