release-version: remove handling for obsolete components

The nar-maven-plugin is named that way a long time already,
the cpptasks-parallel component was merged, and ImageJ2 is
modularized. Therefore it is safe to remove the code to handle the
old versions of said projects.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
check-release: handle SCIFIO correctly

SCIFIO's top-level artifactId starts with 'pom-', but the tags do not
have that prefix (thanks to special handling in the release-version.sh
script). So let's look for the correct tags instead.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>