doc: fix embassy-time doc

[HaoboGu]

Current doc says if there's If no generic-queue-* feature is enabled, a default of 64 timers is used. But according to:

embassy/embassy-time-queue-utils/src/lib.rs

Lines 5 to 13 in 169f9c2

	#[cfg(feature = "_generic-queue")]
	pub mod queue_generic;
	#[cfg(not(feature = "_generic-queue"))]
	pub mod queue_integrated;
	#[cfg(feature = "_generic-queue")]
	pub use queue_generic::Queue;
	#[cfg(not(feature = "_generic-queue"))]
	pub use queue_integrated::Queue;

the queue_integrated::Queue is used in this case. So the default 64 timers actually do nothing:

embassy/embassy-time-queue-utils/src/queue_generic.rs

Lines 112 to 119 in 169f9c2

	#[cfg(not(any(
	feature = "generic-queue-8",
	feature = "generic-queue-16",
	feature = "generic-queue-32",
	feature = "generic-queue-64",
	feature = "generic-queue-128"
	)))]
	const QUEUE_SIZE: usize = 64;