A previous commit changed to use archiveArtifact() to recover CI logs,
and then attempted to "guess" the L1/MAC stats file name through a
regex. However, the format "enb-[0-9]+" is not correct, as
archiveArtifact() puts the task ID ("[0-9]+") BEFORE the file name
(here, "enb"). So, make it more generic and match the final "-enb.log"
("$" means "end of string").

Fixes: 244ea8fc ("Use archiveArtifact() for TerminateeNB()")