Remove "Site" from site title
    
    I finally figured out where this info is stored. This is been a mild
    bother for some time. It makes the title shorter, and it doesn't appear
    in file names or other things if I take screenshots of a docs.fp.o page.
    
    Purely cosmetic, using this change as an excuse to make my first change
    to the production docs.fp.o builder.
    
    Signed-off-by: Justin W. Flory (he/him) <git@jwf.io>