chg: [doc] Added note about 19.04
chg: [doc] Added note about 19.04

MISP/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,FIRSTdotorg/MISP,SteveClement/MISP,SteveClement/MISP,SteveClement/MISP,FIRSTdotorg/MISP,FIRSTdotorg/MISP,MISP/MISP,FIRSTdotorg/MISP,MISP/MISP