Suppress EmptyFunctionBlock detekt violation

In 24abe628 we add updateSecurityLevel and handleOpenSecurityLevelSettingsClicked, but they are only stubs. Later, in d95db65d, we implement those functions.

When we run detekt on 24abe628 the above two functions are reported as violating EmptyFunctionBlock (and we use that that commit because it is the last patch that successfully links with Mozilla's MozAC). Let's clean up this reported violation by suppressing that rule in 24abe628, and then delete it in d95db65d.