POM: remove no-longer-needed code generation logic
POM: remove no-longer-needed code generation logic

All of this configuration moved upstream; see:
https://github.com/scijava/pom-scijava-base/commit/3126d321d5642480f0666a1b5c3f94a1f150a7eb

gab1one/imagej-ops,imagej/imagej-ops