chore: remove WindowUpdateMode::OnReceive

[mxinden]

I suggest we remove WindowUpdateMode::OnReceive in favor of always using (not just defaulting to) WindowUpdateMode::OnRead.

I can not think of a use-case where one would want OnReceive over OnRead. Anyone?

Removing OnReceive will simplify our codebase.

rust-yamux/yamux/src/lib.rs

Lines 66 to 76 in 93b7062

	/// Specifies when window update frames are sent.
	#[derive(Clone, Copy, Debug, PartialEq, Eq)]
	pub enum WindowUpdateMode {
	/// Send window updates as soon as a [`Stream`]'s receive window drops to 0.
	///
	/// This ensures that the sender can resume sending more data as soon as possible
	/// but a slow reader on the receiving side may be overwhelmed, i.e. it accumulates
	/// data in its buffer which may reach its limit (see `set_max_buffer_size`).
	/// In this mode, window updates merely prevent head of line blocking but do not
	/// effectively exercise back pressure on senders.
	OnReceive,

[thomaseizinger]

Sounds good to me!

Perhaps make a point-release deprecating it first :)