Removes unused SecurityExchange methods
Removes unused SecurityExchange methods

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