Update PersistentHarvestingDelegationMessage.ts

[44uk]

Fix TypeDoc comment.

[coveralls]

Pull Request Test Coverage Report for Build 784

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 782:	0.0%
Covered Lines:	10
Relevant Lines:	10

---

💛 - Coveralls

[fboucquez]

Thanks @44uk !