message: minor tweak to concept Advanceable
diff: @@ -91,9 +91,9 @@ namespace ranges
  j - j,
  i += n,
  i -= n,
  - static_cast<I>(i - n),
  - static_cast<I>(i + n),
  - static_cast<I>(n + i),
  + static_cast<I>(j - n),
  + static_cast<I>(j + n),
  + static_cast<I>(n + j),
  // NOT TO SPEC:
  // Unsigned integers are advanceable, but subtracting them results in
  // an unsigned integral, which is not the same as the difference type,
  