correct the comments (nim-lang#19322)

--expandArc

```
var
  a
  b
a = matrix(5, 5, 1.0)
b = matrix(5, 5, 2.0)
`=sink`(b, -
  let blitTmp = b
  wasMoved(b)
  blitTmp +
    a)
`=destroy`(b)
`=destroy`(a)
```

compiler/optimizer.nim

@@ -127,11 +127,11 @@ proc analyse(c: var Con; b: var BasicBlock; n: PNode) =
         for i in 0 ..< n.len:
           analyse(c, b, n[i])
       else:
-        #[ Test tmatrix.test3:
+        #[ Test destructor/tmatrix.test3:
         Prevent this from being elided. We should probably
         find a better solution...
 
-            `=sink`(b, - (
+            `=sink`(b, -
               let blitTmp = b;
               wasMoved(b);
               blitTmp + a)