Fixes Delisting bug
Fixes Delisting bug

Reverts commit f4abe9ce

Now delisted securities are removed using IAlgorithm.RemoveSecurity that properly removes a security from a SecurityManager: keeps it at the Portfolio, but remove it from the user universe, unsubscribing to the datafeed in the process.

kaffeebrauer/Lean,kaffeebrauer/Lean,QuantConnect/Lean,young-zhang/Lean,andrewhart098/Lean,AlexCatarino/Lean,AnshulYADAV007/Lean,JKarathiya/Lean,andrewhart098/Lean,kaffeebrauer/Lean,AlexCatarino/Lean,JKarathiya/Lean,AnshulYADAV007/Lean,StefanoRaggi/Lean,Jay-Jay-D/LeanSTP,devalkeralia/Lean,QuantConnect/Lean,Mendelone/forex_trading,StefanoRaggi/Lean,young-zhang/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,StefanoRaggi/Lean,Mendelone/forex_trading,kaffeebrauer/Lean,redmeros/Lean,QuantConnect/Lean,Jay-Jay-D/LeanSTP,tomhunter-gh/Lean,Phoenix1271/Lean,Mendelone/forex_trading,tomhunter-gh/Lean,redmeros/Lean,Phoenix1271/Lean,Jay-Jay-D/LeanSTP,Jay-Jay-D/LeanSTP,Mendelone/forex_trading,Phoenix1271/Lean,jameschch/Lean,AlexCatarino/Lean,redmeros/Lean,devalkeralia/Lean,QuantConnect/Lean,JKarathiya/Lean,young-zhang/Lean,JKarathiya/Lean,jameschch/Lean,devalkeralia/Lean,jameschch/Lean,AnshulYADAV007/Lean,StefanoRaggi/Lean,young-zhang/Lean,jameschch/Lean,kaffeebrauer/Lean,jameschch/Lean,tomhunter-gh/Lean,Phoenix1271/Lean,tomhunter-gh/Lean,Jay-Jay-D/LeanSTP,AnshulYADAV007/Lean,AnshulYADAV007/Lean,andrewhart098/Lean,andrewhart098/Lean,devalkeralia/Lean,redmeros/Lean