fix: Update dynamic-on-time component to allow for ESPHome 2026.2.0

The `dynamic-on-time component` was updated to 1.2.1 fixing errors
when using ESPHome 2026.2.0
(see hostcc/esphome-component-dynamic-on-time#40)

Author: hostcc

schedule.yaml

@@ -204,7 +204,7 @@ number:
     mode: box
 
 external_components:
-  - source: github://hostcc/esphome-component-dynamic-on-time@1.2.0
+  - source: github://hostcc/esphome-component-dynamic-on-time@1.2.1
 
 dynamic_on_time:
   - id: lawn_schedule