fix(least_squares): Wrap unsafe cast in trusted

[Geod24]

Buildkite is hitting this issue:

source/mir/optim/least_squares.d(242,6): Error: `@safe` function `mir.optim.least_squares.__unittest_L219_C7` cannot call `@system` function `mir.optim.least_squares.__unittest_L219_C7.optimize!((x, y)
--
  | {
  | y[0] = x[0];
  | y[1] = 2 - x[1];
  | }
  | , (x, J)
  | {
  | J[0, 0] = 1;
  | J[0, 1] = 0;
  | J[1, 0] = 0;
  | J[1, 1] = -1;
  | }
  | , null, double).optimize`
  | )(settings, 2, x, l, u);
  | ^
  | source/mir/optim/least_squares.d(176,15):        and cast from `immutable(Exception)` to `object.Exception` makes it fail to infer `@safe`
  | throw cast()leastSquaresException_maxIterations;
  | ^

[Geod24]

FYI @9il : https://buildkite.com/dlang/dub/builds/3945#01970814-0fe9-43eb-8fc8-a25f160ba1e3

[9il]

Thank you!

[9il]

v2.0.8

[Geod24]

@9il : I don't see the commit on master, and v2.0.8 is on the same commit as v2.0.7 so I think you accidentally reverted this.

[9il]

omg, sorry about that, v2.0.9