[Migration] - Remove legacy code parts: Stale NUKE_ENTERPRISE_TOKEN handling in bootstrapper files

[ITaluone]

Description

Previous version of NUKE added a check for NUKE_ENTERPRISE_TOKEN and adds a special nuget feed in build.sh and build.ps1.

I propose to let the migration get rid of this because:

• At time of writing there is no plan go commercial
• If this env var is set for some users, they will not have an advantage, since this feed at least is stale, at worst non existent anymore

Usage Example

Just with the common fallout-migrate command doing its work

Alternative

Leave as is, let the user remove this when they step over. But why don't give the users a service by removing legacy code parts?

Could you help with a pull-request?

Yes