When a sender calls CloseNotification (per freedesktop spec) for a
persistent notification (expire-timeout=0), the onDropped handler
removed the wrapper from internal arrays but did not dismiss the
visible popup. The popup remained on screen forever for non-critical
notifications like YubiKey touch prompts.
Set wrapper.popup=false in onDropped so the popup exits via the
normal signal chain. This is minimal; it does not change timeout
handling, queue management, or the isPersistent marker.
Also reverts the previous workaround that special-cased non-critical
expireTimeout=0 to use DMS timeout. Upstream spec-correct behavior
is to honor the sender timeout, and fix the dismissal bug instead.
Closes#2814