Make the build closer to reproducible

This bumps to pom-fiji 5.0.6, which upgrades the TrackMate
component to 2.6.1, its first non-tainted release.

It eliminates the following errors:

    $ mvn org.scijava:scijava-maven-plugin:0.3.0:verify-no-snapshots
    [ERROR] Could not resolve dependency: Dependency {groupId=sc.fiji, artifactId=fiji-lib, version=2.0.0, type=jar} of path:
            sc.fiji:VIB-lib:2.0.0
            sc.fiji:3D_Viewer:3.0.0
            sc.fiji:TrackMate_:2.6.0
            sc.fiji:TrackMate_examples:1.0.3-SNAPSHOT
    [ERROR] Found SNAPSHOT version:
            sc.fiji:pal-optimization:2.0.0-SNAPSHOT
            sc.fiji:VIB-lib:2.0.0
            sc.fiji:3D_Viewer:3.0.0
            sc.fiji:TrackMate_:2.6.0
            sc.fiji:TrackMate_examples:1.0.3-SNAPSHOT
    [ERROR] Found SNAPSHOT parent:
            sc.fiji:pom-fiji:2.0.0-SNAPSHOT
            sc.fiji:pal-optimization:2.0.0-SNAPSHOT
            sc.fiji:VIB-lib:2.0.0
            sc.fiji:3D_Viewer:3.0.0
            sc.fiji:TrackMate_:2.6.0
            sc.fiji:TrackMate_examples:1.0.3-SNAPSHOT

Note that there are still many errors relating to third party
components, but none left regarding tainted SciJava releases.