Logout screen: rephrase "update and perform [session action]" labels

Reason for the change

Remove the "now" since what will actually happen now is update, not the session action.

Replace the ampersand with the word "and" as ampersands are typically used in titles and more formal writing, not in descriptions of actions.

Test plan

Have a pending offline update and click Update or Restart in Kickoff.

Screenshots or screen recordings

Bugs fixed

N/A

@teams/vdg