clang-format: Improve indentation of comments in expressions.

Before:
  int i = (a)
              // comment
          + b;
  return aaaa == bbbb
                 // comment
             ? aaaa
             : bbbb;
After:
  int i = (a)
          // comment
          + b;
  return aaaa == bbbb
             // comment
             ? aaaa
             : bbbb;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221985 91177308-0d34-0410-b5e6-96231b3b80d8