Ignore ref-updated event in doc builds

The RTDv3 template by default listens for tag push events
(ref-updated events), but the O-RAN-SC doc process has no need
at present. Ignore to skip unnecessary builds at readthedocs.io.

Also renamed the directory and file to match the actual job prefix.

Signed-off-by: Lott, Christopher (cl778h) <cl778h@att.com>
Change-Id: I6e5f1f03ad639ca92aa72b353bb0e533571af748