qt-everywhere-src-5.15.x-attributions.pdf: Add Apache 2.0 license appendix

Under the "Android Billing API Library" section, there are multiple instances of the Apache 2.0 license text that don't include the appendix (see the bottom of https://www.apache.org/licenses/LICENSE-2.0.txt for the appendix text).

In contrast, attributions of other libraries (that are licensed under Apache 2.0) do include the appendix.

A customer has requested that the attributions document be amended so that the appendix is included with all copies of the Apache 2.0 license text.