quasi-typo: stray backslash

backslash may have been there to escape italicization, but that's
unnecessary in GitHub's Markdown dialect and looks weird on the
site. Gruber's Perl implementation might have perf advantages but
I think represents a dead (or at best, classical) variant of the
micro-language at this point.

weirdly enough, the matching backslash in the header above my edit
seems to render just fine. #lolgithub I guess.