m: remove references to LUK, GUK

This unifies the unlock key nomenclature throughout the repository:
- Local Unlock Key becomes a Node Unlock Key
- Global Unlock Key becomes a Cluster Unlock Key

Change-Id: I674ad68a50b3845705f3e2c57952fc7fba5be665
Reviewed-on: https://review.monogon.dev/c/monogon/+/816
Reviewed-by: Sergiusz Bazanski <serge@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/proto/common/common.proto b/metropolis/proto/common/common.proto
index 15dc9e3..c25736b 100644
--- a/metropolis/proto/common/common.proto
+++ b/metropolis/proto/common/common.proto
@@ -64,7 +64,7 @@
     // NEW: the node has established a first contact with the cluster and
     // intends to register into it. The node's identity has not been verified
     // and no hardware attestation of the new node was performed.
-    // The node has generated a CUK/LUK and set up storage encrypted with the
+    // The node has generated a CUK/NUK and set up storage encrypted with the
     // combination of both keys.
     // The node has generated a private/public keypair, and that keypair has
     // been used to contact the already running Cluster.