clang-format: Row back on the AlwaysBreakBeforeMultilineStrings change.

It was a bit too aggressive.

With this patch, we keep on breaking here:
  aaaaaaaaaaaaa(aaaaaaa,
                "aaaaaaa"
                "bbbbbbb");

But don't break in:
  aaaaaaaaaaaaa(aaaaaaa, aaaaaaaa("aaaaaaa"
                                  "bbbbbbb"));

llvm-svn: 240024