[lld-macho][docs] Cosmetic changes

1. Fixed rST hyperlink syntax
2. Renamed LD64 -> ld64
3. Moved up the `-no_deduplicate` section so it is right under the
   section talking about how our default dedup behavior differs; IMO
   it makes more sense to read them in that order
4. De-bullet-listed some other sections so we have less whitespace in
   the rendered page
5. Since the Mach-O LLD Port page has only one sub-page, don't render an
   entire toctree with just one item. Use a "See also" box instead.
6. Wrap lines at 80 chars.

Reviewed By: #lld-macho, thevinster

Differential Revision: https://reviews.llvm.org/D133717