Update "About" of aasx package explorer

[BirgitBoss]

Change

The AASX Package Explorer is a sample application for demonstration of the
features of the Asset Administration Shell.
The implementation uses the concepts of the document "Details of the Asset
Administration Shell" published on www.plattform-i40.de which is licensed
under Creative Commons CC BY-ND 3.0 DE.

to

The AASX Package Explorer is a sample application for demonstration of the
features of the Asset Administration Shell.
The implementation uses the concepts of the "Asset
Administration Shell Specifications" published on [www.plattform-i40.de](https://industrialdigitaltwin.org/en/content-hub/aasspecifications) which are licensed
under Creative Commons CC-BY-4.0.