Revert "Make voicemail notification dismissable"

Voicemail notification is required to be a non-dismissable alert for some carriers.

This reverts commit 44be27432a984f9072150c9525477e54cbfe96fd

Bug: 7888110
Change-Id: Iaf6523cff53850422ab06c2c80cc30c6b2987499
2 files changed