clang-format: Fix bug in column layout.

Before (with 60 character limit in Google style):
  return {
      {aaaaaaaaaaaaaaaaaaaaaaaaa}, {aaaaaaaaaaaaaaaaa},
      {aaaaaaaaaaaaaaaaaaaaaaaaa}, {aaaaaaaaaaaaaaaaa}};
After:
  return {{aaaaaaaaaaaaaaaaaaaaaaaaa}, {aaaaaaaaaaaaaaaaa},
          {aaaaaaaaaaaaaaaaaaaaaaaaa}, {aaaaaaaaaaaaaaaaa}};