chore: retire pfv-tsys8 and fix stale host-skip comment in deploy-check.sh

pfv-tsys8 is permanently retired. Strike its only doc reference and
correct the stale comment in perf/deploy-check.sh that wrongly listed
pfv-tsys9 as "off the air" (tsys9 is online and in the host array;
tsys8 is the retired host).

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

perf/deploy-check.sh

@@ -6,8 +6,8 @@
 # read-only, and pulls the resulting log back to returned-logs/.
 #
 # EXPLICITLY SKIPS:
-#   - pfv-tsys2   (off the air per user)
-#   - pfv-tsys9   (off the air per user; also not in original inventory)
+#   - pfv-tsys2   (off the air per user; Win10 pending rebuild)
+#   - pfv-tsys8   (retired / permanently offline per user)
 #
 # Safety features:
 #   - BatchMode=yes        : never hang on a password prompt