* time.c (rb_time_unmagnify_to_float): Avoid double rounding.
  Reported by Tsuyoshi Sawada.
  https://bugs.ruby-lang.org/issues/10135#note-1



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47289 b2dd03c8-39d4-4d8f-98ff-823fe69b080e