Fix warnings

Since pom-fiji depends on pom-imagej, we do not need to specify a
couple of dependency versions anymore; they are managed by pom-imagej
now.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Let pom-imagej manage which ImageJ 1.x version we use

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