Rephrase dialog message of clear storage dialog for security concern am: 6024ea55 am: 2d08d347 am: ebcc8d97

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/16101567

Change-Id: I420dae4bb862e6ff4c7178d2df2668f92a92439f