Update PIP-42.md

[hrook1]

Updates new Stakemanager address in the Abstract.

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [ ] New PIP
• [x] Revision to an existing PIP
• [ ] This change requires a documentation update
• [ ] My edit follows the style guidelines