Revert "Issue #2822382 by voleger, pfrenssen, erozqba, RytoEX, borisson_, sidharthap, Jo Fitzgerald, shashikant_chauhan: Make every  property protected on classes extending BrowserTestBase and KernelTestBase"

This reverts commit 29d0958a.

Issue #2822382 by voleger, pfrenssen, erozqba, RytoEX, borisson_, sidharthap, Jo Fitzgerald, shashikant_chauhan: Make every  property protected on classes extending BrowserTestBase and KernelTestBase

(cherry picked from commit 69501f30)

Issue #2352791 by prics, sam0971, naveenvalecha, Ashish.Dalvi, dstotijn, ZeiP, Mile23, tim.plunkett: Add test coverage for admin/structure/block/demo