[core] Drop unused DELAY_ACTION from InternalSchedulerID enum

Followup to #16129. DelayAction now keys its scheduler entry by
self-pointer (NameType::SELF_POINTER), so the DELAY_ACTION enum
value is no longer referenced anywhere.

esphome/core/component.h

@@ -65,7 +65,6 @@ inline constexpr uint32_t SCHEDULER_DONT_RUN = 4294967295UL;
 /// with component-level NUMERIC_ID values, even if the uint32_t values overlap.
 enum class InternalSchedulerID : uint32_t {
   POLLING_UPDATE = 0,  // PollingComponent interval
-  DELAY_ACTION = 1,    // DelayAction timeout
 };
 
 // Forward declaration