Bump commercial to v19.6.0

Seen on FRONTS-PROD, ADMIN-PROD (merged by @emma-imber 16 minutes and 52 seconds ago)

Check your changes on www.theguardian.com ✔️
Keep an eye on the deploy dashboard&_a=(description:'',filters:!(),fullScreenMode:!f,options:(darkTheme:!f,useMargins:!f),panels:!((gridData:(h:4,i:'4',w:6,x:6,y:0),id:'735f9ce0-4a04-11e7-9f15-395e2d1c9b1f',panelIndex:'4',type:visualization,version:'6.2.4'),(gridData:(h:4,i:'5',w:6,x:0,y:0),id:b9249830-4a03-11e7-91e8-2fbfd59c38bb,panelIndex:'5',type:visualization,version:'6.2.4'),(gridData:(h:4,i:'7',w:6,x:0,y:4),id:ac507b90-4a0f-11e7-9f15-395e2d1c9b1f,panelIndex:'7',type:visualization,version:'6.2.4'),(gridData:(h:4,i:'9',w:6,x:6,y:4),id:a5f78860-4ad2-11e7-9930-73b4968e85d8,panelIndex:'9',type:visualization,version:'6.2.4')),query:(language:lucene,query:(query_string:(analyze_wildcard:!t,query:'stage:PROD%20NOT%20app:preview'))),timeRestore:!f,title:'Frontend%20PROD%20Deploy',viewMode:view)) 📉

guardian / frontend