[clang-format] [NFC] update the documentation in Format.h to allow...

[clang-format] [NFC] update the documentation in Format.h to allow dump_format_style.py to get a little closer to being correct.

Summary:
Running dump_format_style.py on the tip of the trunk causes ClangFormatStyleOptions.rst to have changes, which I think ideally it shouldn't.

Some recent commits have meant Format.h and ClangFormatStyleOptions.rst have become out of sync such that dump_format_style.py either couldn't be run or generated incorrect .rst files.

It's also important to remember to edit the IncludeStyles from Tooling.

Make a couple of changes {D6833} {D64695} which came from recent clang-format commits that missed this step. There are still a couple of other changes  from commit {D67541} {D68296} which also need to be looked at, but I'd like to park these first two changes first.

The authors of these original commits I've included in the reviewers, I'm happy to work on the changes, just really need to know which is the ground truth of the changes you want to keep (whats in the Format.h) or what is in the ClangFormatStyleOptions.rst

Reviewers: klimek, mitchell-stellar, owenpan, jvoung, Manikishan, sammccall

Reviewed By: mitchell-stellar

Subscribers: cfe-commits

Tags: #clang-format, #clang

Differential Revision: https://reviews.llvm.org/D69404