README.md: remove Bio-Formats from the table

The Bio-Formats Maven-based build system (which is maintained in
parallel with Ant) stopped using pom-scijava as its parent POM; see:

    https://github.com/openmicroscopy/bioformats/commit/45eea534842c1edfebec56ab72653dba4cc53057

So it is no longer accurate for it to be included in the table here.

See also discussion at:

    https://github.com/openmicroscopy/bioformats/pull/951