Rephrase dialog message of clear storage dialog for security concern am: 881d7ec5 am: 0549b8c4 am: 82872a85

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/16101566

Change-Id: I7c73f39e9ab8592e1f289e2ea31bbc0e84368816