Document invariant violation found by fuzzer
Document invariant violation found by fuzzer

If-def'ed out by default so that the remaining tests pass.

Output:

```
F20220812 00:05:11.462432    12 token_partition_tree.cc:63] Check failed: parent_begin == children_begin (2 vs. 3) node:
{ (>>>>>>>>[<auto>], policy: append-fitting-sub-partitions) @{0,1,1,0}, (origin: "`c()")
  { (>>>>>>>>[(], policy: fit-else-expand, (origin: "(")) }
  { (>>>>>>>>[)], policy: fit-else-expand, (origin: "")) }
}
```

Signed-off-by: Henner Zeller <259ad50fabbfd39355f36ecd6c0afca541ea66ef@acm.org>

chipsalliance/verible,chipsalliance/verible,chipsalliance/verible,chipsalliance/verible,chipsalliance/verible