Bump pom-scijava version

This developer is too tired right now, after fixing so many bugs and
not getting any real work done today, to find out why IJ2 requiring
1.31 and Fiji requiring 1.27 of pom-scijava ends up in both agreeing
to use 1.27 instead of 1.31. Later. This fixes Jenkins for now.

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