docs(runbooks): two more uncited "4-minute" claims the first pass missed

A systematic grep for the TTL assertion found it still in runbooks/README.md and in
runbooks/kustomization.yaml, outside the page being rewritten. Same correction: the
countdown on plex.tv/claim is the authority, not a number in our tree.

README.md also now records that the server is CLAIMED and points at claim-ship.sh with
the measured ~2m45s loop, rather than describing a push-based sequence that no longer
exists.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

runbooks/kustomization.yaml

@@ -83,7 +83,7 @@ configMapGenerator:
       - node-memory-swap=node-memory-swap.md
       # Operator procedure, not an alert page (no alert links to it — the
       # alert-runbooks-resolvable check treats that as advisory). It is served
-      # because the 4-minute plex.tv claim window is not a thing to go looking
+      # because the plex.tv claim window is short and is not a thing to go looking
       # for in git: /runbooks/plex-claim has to resolve the moment it is needed.
       - plex-claim=plex-claim.md
       - pvc-capacity=pvc-capacity.md