Improve formatting for do expressions

[sosukesuzuki]

Prettier 2.2.1
Playground link

--parser babel

Input:

expect(do {
  var bar = "foo";
  bar;
}).toBe("foo");

Output:

expect(
  do {
    var bar = "foo";
    bar;
  }
).toBe("foo");

Expected behavior:
Same as input

expect(do {
  var bar = "foo";
  bar;
}).toBe("foo");

Additional context:

Original was reported by @nicolo-ribaudo at babel/babel#13122 (comment)