In the "Metacharacters and Escapes" section of regexp.rdoc, it said that
to match a backslash literally, it must be backslash-escaped, but the
rendered HTML showed three backslashes (\\\). There should only be two
backslashes (\\).

patched by jlmuir (J. Lewis Muir) [fix GH-1677]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60326 b2dd03c8-39d4-4d8f-98ff-823fe69b080e