Polish variable name in ReschedulingRunnable

As a variable name, `initDelay` is applicable for `scheduleAtFixedRate`
and `scheduleWithFixedDelay` but not for `schedule`.

Closes gh-30762

Author: quaff

spring-context/src/main/java/org/springframework/scheduling/concurrent/ReschedulingRunnable.java

@@ -79,8 +79,8 @@ public ScheduledFuture<?> schedule() {
 			if (this.scheduledExecutionTime == null) {
 				return null;
 			}
-			Duration initialDelay = Duration.between(this.triggerContext.getClock().instant(), this.scheduledExecutionTime);
-			this.currentFuture = this.executor.schedule(this, initialDelay.toNanos(), TimeUnit.NANOSECONDS);
+			Duration delay = Duration.between(this.triggerContext.getClock().instant(), this.scheduledExecutionTime);
+			this.currentFuture = this.executor.schedule(this, delay.toNanos(), TimeUnit.NANOSECONDS);
 			return this;
 		}
 	}