clang-format: Make indentation after "<<" more consistent.

Before:
  Diag(aaaaaaaaaaaaaaaaaaaa, aaaaaaaa)
      << aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
	  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);
  Diag(aaaaaaaaaaaaaaaaaaaa, aaaaaaaa)
      << aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
	     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
      << aaa;

After:
  Diag(aaaaaaaaaaaaaaaaaaaa, aaaaaaaa)
      << aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
	     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);
  Diag(aaaaaaaaaaaaaaaaaaaa, aaaaaaaa)
      << aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
	     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
      << aaa;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@260517 91177308-0d34-0410-b5e6-96231b3b80d8