Add some missing localized strings

toolkit/components/passwordmgr/resources/locale/passwordmgr.properties

@@ -41,3 +41,6 @@ savePasswordTitle = Confirm
 savePasswordText = Password Manager can remember this logon and enter it automatically the next time you return to this website.\nDo you want Password Manager to remember this logon?
 neverForSite = Never for this site
 close = Close
+passwordChangeTitle = Confirm Password Change
+passwordChangeText = Would you like to have Password Manager change the stored password for %S?
+userSelectText = Please confirm which user you are changing the password for