picking: Avoid deprecated header.
picking: Avoid deprecated header.

Since mosra/magnum@73419be9e6506ce84e69ad8f6baafedeada7ddb2, `Camera3D.h`
is deprecated in favour of `Camera.h`.

Signed-off-by: Squareys <0f6a03d4883e012ba4cb2c581a68f35544703cd6@googlemail.com>

mosra/magnum-examples,mosra/magnum-examples,Squareys/magnum-examples,Squareys/magnum-examples,Squareys/magnum-examples,mosra/magnum-examples,mosra/magnum-examples,mosra/magnum-examples,mosra/magnum-examples,mosra/magnum-examples,Squareys/magnum-examples