small fix to AngleAxisTemplate<Scalar>::angle() fct

Small fix to adjust when angle is above PI.
Hi all,
This is not a good fix! For example, it doesn't deal with negative angles larger than 2 pi. If you really need the angle constrained to `(-pi, pi]`, use`` aa.setUnique().angle()``.

See:  https://github.com/ethz-asl/minkindr/blob/master/minkindr/include/kindr/minimal/implementation/angle-axis-inl.h#L102-L134

And for wrapping angles: https://github.com/ethz-asl/Schweizer-Messer/blob/master/sm_kinematics/src/rotations.cpp#L159-L162

Can you please revert this change?

Thanks!