Update milestones for May (dotnet#61285)

Author: wtgodbe

.github/policies/resourceManagement.yml

@@ -551,7 +551,7 @@ configuration:
       then:
       - removeMilestone
       - addMilestone:
-          milestone: 9.0.4
+          milestone: 9.0.5
       description: '[Milestone Assignments] Assign Milestone to PRs merged to release/9.0 branch'
     - if:
       - payloadType: Pull_Request
@@ -562,7 +562,7 @@ configuration:
       then:
       - removeMilestone
       - addMilestone:
-          milestone: 8.0.15
+          milestone: 8.0.16
       description: '[Milestone Assignments] Assign Milestone to PRs merged to release/8.0 branch'
     - if:
       - payloadType: Issues