Update INSTALL-RHEL.md
Update INSTALL-RHEL.md

Edited subheaders with caps for #### level headers as they're nesting in RTD
projectjellyfish/api,dcallner/project-jellyfish-api,stackus/api,AllenBW/api,boozallen/projectjellyfish,dcallner/project-jellyfish-api,adderall/api,mafernando/api,sonejah21/api,adderall/api,adderall/api,sreekantch/JellyFish,AllenBW/api,boozallen/projectjellyfish,stackus/api,mafernando/api,boozallen/projectjellyfish,sonejah21/api,projectjellyfish/api,sreekantch/JellyFish,dcallner/project-jellyfish-api,boozallen/projectjellyfish,sreekantch/JellyFish,stackus/api,sonejah21/api,mafernando/api,projectjellyfish/api,AllenBW/api