Design Repository Migration has been deprecated as of Siebel 19.3

Design Repository Migration won't be available from Siebel 19.3 update.
For more details:
Refer: 2531821.1

Oracle Product Management / Oracle Engineering removed the Design Repository migration from Siebel 19.3 onwards as there will only be one Design Repository. Bug 29178365 - REMOVE THE DESIGN REPOSITORY MIGRATION SERVICE FROM MIGRATION UI