[core] Drop static on shrink_scheduler_vector_ for clang-tidy compliance

Project's .clang-tidy applies different naming rules to static methods
(ClassMethodCase, no suffix) vs instance methods (PrivateMethodCase /
ProtectedMethodCase, _ suffix required). The helper had a trailing _ but
was static, so clang-tidy flagged it. Drop static -- the helper is already
noinline'd and called only at trim time, so the hidden this arg is free
in any meaningful sense.

esphome/core/scheduler.h

@@ -367,7 +367,7 @@ class Scheduler {
  private:
   // Out-of-line helper that shrinks a SchedulerItem* vector's capacity to its current
   // size. Centralised so trim_freelist() doesn't pay flash cost per call site.
-  static void shrink_scheduler_vector_(std::vector<SchedulerItem *> *v);
+  void shrink_scheduler_vector_(std::vector<SchedulerItem *> *v);
 
   // Helper to cancel matching items - must be called with lock held.
   // When find_first=true, stops after the first match (used by set_timer_common_ where