Remove JDK 7 from build documentation. (#6031)
Remove JDK 7 from build documentation. (#6031)

See issue #6030
michaelschiff/druid,himanshug/druid,deltaprojects/druid,mghosh4/druid,gianm/druid,Fokko/druid,mghosh4/druid,michaelschiff/druid,druid-io/druid,knoguchi/druid,monetate/druid,leventov/druid,Fokko/druid,liquidm/druid,Fokko/druid,Fokko/druid,gianm/druid,jon-wei/druid,gianm/druid,leventov/druid,liquidm/druid,nishantmonu51/druid,gianm/druid,nishantmonu51/druid,monetate/druid,druid-io/druid,jon-wei/druid,Fokko/druid,jon-wei/druid,dkhwangbo/druid,pjain1/druid,knoguchi/druid,implydata/druid,monetate/druid,deltaprojects/druid,pjain1/druid,dkhwangbo/druid,himanshug/druid,michaelschiff/druid,pjain1/druid,mghosh4/druid,mghosh4/druid,dkhwangbo/druid,monetate/druid,druid-io/druid,michaelschiff/druid,liquidm/druid,liquidm/druid,deltaprojects/druid,jon-wei/druid,mghosh4/druid,gianm/druid,pjain1/druid,mghosh4/druid,knoguchi/druid,nishantmonu51/druid,implydata/druid,monetate/druid,jon-wei/druid,implydata/druid,deltaprojects/druid,druid-io/druid,dkhwangbo/druid,implydata/druid,jon-wei/druid,michaelschiff/druid,knoguchi/druid,dkhwangbo/druid,gianm/druid,gianm/druid,himanshug/druid,himanshug/druid,pjain1/druid,monetate/druid,nishantmonu51/druid,knoguchi/druid,michaelschiff/druid,implydata/druid,himanshug/druid,liquidm/druid,druid-io/druid,liquidm/druid,michaelschiff/druid,leventov/druid,mghosh4/druid,deltaprojects/druid,implydata/druid,Fokko/druid,pjain1/druid,nishantmonu51/druid,deltaprojects/druid,pjain1/druid,deltaprojects/druid,nishantmonu51/druid,leventov/druid,jon-wei/druid,monetate/druid,nishantmonu51/druid,leventov/druid,Fokko/druid