Rephrase dialog message of clear storage dialog for security concern am:...

Rephrase dialog message of clear storage dialog for security concern am: 7d22136f am: 337e182e am: d67d983b am: 7f972fc6 am: 60fcac57 am: 103032e2 am: bb65a1a3

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/16101568

Change-Id: I79b2825ae54d53e9051034d9adc6b024832dc4d2