clang-format: [JS] Support destructuring assignments in for loops.

Before:
  for (let { a, b } of x) {
  }

After:
  for (let {a, b} of x) {
  }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@262776 91177308-0d34-0410-b5e6-96231b3b80d8