Removing a file from a protected folder in Mojave
You can remove the file without disabling SIP by booting to Recovery and then deleting the file in the terminal. The system disk is actually mounted read/write in Mojave Recovery, so the trick is that you have to refer to the drive by starting at /Volumes/yourdrivenamehere.  So in this case the command to remove the file would be:

rm -rf /Volumes/yourdrivenamehere/Library/SystemMigration/History/Migration-1C2FCFF8-A394-409D-8DB3-E7885C0D5E81/QuarantineRoot/Library/StagedExtensions/Library/Extensions/Soundflower.kext