cloud_storage/partition_recovery_manager: some include hygiene

[andijcr]

a small unused header cleanup on partition_recovery_manager.{h,cc}

Backports Required

• [x] none - not a bug fix
• [ ] none - issue does not exist in previous branches
• [ ] none - papercut/not impactful enough to backport
• [ ] v22.3.x
• [ ] v22.2.x
• [ ] v22.1.x

Release Notes

• none