Fix maturityLevel of loki, metrics-server, and vault

General MR

Summary

The following packages live under projects/graduated but did not update their maturityLevel to graduated.

• loki
• metrics-server
• vault

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Linked Issue

issue

Upgrade Notices

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projects/graduated/loki.yaml

@@ -25,7 +25,7 @@ metadata:
   - Apache 2.0
 
   # Maturity level of the package
-  maturityLevel: Incubating # Sandbox, Incubating, or Graduated
+  maturityLevel: Graduated # Sandbox, Incubating, or Graduated
 
   # Maintenance Track of the package
   maintenanceTrack: BigBangIntegrated # BigBangIntegrated, BigBangMaintained, CommunityMaintained