Replace "Stand-by" and "Off" with common states in palazzetti (#141809)

Also fixes the  wrong spelling of "Stand-by" by using "Standby" from the common string.

homeassistant/components/palazzetti/strings.json

@@ -74,7 +74,7 @@
       "status": {
         "name": "Status",
         "state": {
-          "off": "Off",
+          "off": "[%key:common::state::off%]",
           "off_timer": "Timer-regulated switch off",
           "test_fire": "Ignition test",
           "heatup": "Pellet feed",
@@ -83,7 +83,7 @@
           "burning": "Operating",
           "burning_mod": "Operating - Modulating",
           "unknown": "Unknown",
-          "cool_fluid": "Stand-by",
+          "cool_fluid": "[%key:common::state::standby%]",
           "fire_stop": "Switch off",
           "clean_fire": "Burn pot cleaning",
           "cooling": "Cooling in progress",