Update apps-apis.md
Update apps-apis.md

changed "subsytem" to "subsystem".

khorne3/docs,Annyv2/docs,hamzawi06/docs,auth0/docs,Catografix/docs,sandrinodimattia/docs,yvonnewilson/docs,jeffreylees/docs,miparnisari/docs,hamzawi06/docs,khorne3/docs,sandrinodimattia/docs,sandrinodimattia/docs,yvonnewilson/docs,Annyv2/docs,Annyv2/docs,Catografix/docs,hamzawi06/docs,auth0/docs,khorne3/docs,auth0/docs,yvonnewilson/docs,jeffreylees/docs,Catografix/docs,jeffreylees/docs