message: complex: Simplify the from_str signature
diff: @@ -748,7 +748,7 @@ impl<T> FromStr for Complex<T> where
  type Err = ParseComplexError<T::Err>;
  /// Parses `a +/- bi`; `ai +/- b`; `a`; or `bi` where `a` and `b` are of type `T`
  - fn from_str(s: &str) -> Result<Complex<T>, ParseComplexError<T::Err>>
  + fn from_str(s: &str) -> Result<Self, Self::Err>
  {
  let imag = match s.rfind('j') {
  None => 'i',
  