make orchestrator-core==2.7.5

@karel.vanklink I just checked orchestrator-core's code again and this code has been around since 2.2 so I am surprised now!

requirements.txt

-orchestrator-core==2.6.1
+orchestrator-core==2.7.5
 requests==2.31.0
 infoblox-client~=0.6.0
 pycountry==23.12.11