Add Darwin availability annotation for new Thermostat feature bit. (#26823)

This was added in https://github.com/project-chip/connectedhomeip/pull/26686
diff --git a/src/darwin/Framework/CHIP/templates/availability.yaml b/src/darwin/Framework/CHIP/templates/availability.yaml
index b879c18..bf83346 100644
--- a/src/darwin/Framework/CHIP/templates/availability.yaml
+++ b/src/darwin/Framework/CHIP/templates/availability.yaml
@@ -7779,6 +7779,9 @@
           Scenes:
               Feature:
                   - SceneNames
+          Thermostat:
+              Feature:
+                  - LocalTemperatureNotExposed
           HEPAFilterMonitoring:
               Feature:
                   - Condition