Clarify that package.order does not affect visibility

[henrikt-ma]

Addressing a small need for clarification encountered in relation to #3921.

[maltelenz]

Seems fine to me.

[HansOlsson]

The text is fine in itself. However, I had to check what and where it was already present and found:

https://specification.modelica.org/master/class-predefined-types-and-declarations.html#access-control-public-and-protected-elements

All elements defined under the heading protected are regarded as protected. All other elements (i.e.,
defined under the heading public, without headings or in a separate file) are public (i.e., not protected).

So, perhaps we should make it clear that it was already defined (not exactly sure how to formulate):

Suggested change

	Only elements defined in \filename{package.mo} are affected by the visibility control (\cref{access-control-public-and-protected-elements}) in \filename{package.mo}; the child classes defined in other files or directories always have public visibility.
	In particular, reordering classes using \filename{package.order} has no impact on visibility.
	According to \cref{access-control-public-and-protected-elements} only elements defined in \filename{package.mo} are affected by the visibility control in \filename{package.mo}; the child classes defined in other files or directories always have public visibility.
	In particular, reordering classes using \filename{package.order} has no impact on visibility.