Bump milestone tracking for merged PRs to 17.12

`main` is now targeting 17.12. Update the config so that merged PRs are incorrectly assigned to the 17.11 milestone on GitHub.

This helps prevent confusion about what VS version a fix is in.

.github/policies/resourceManagement.yml

@@ -74,7 +74,7 @@ configuration:
           branch: main
       then:
       - addMilestone:
-          milestone: 17.11
+          milestone: 17.12
       description: Milestone tracking - main
       triggerOnOwnActions: true