Doc: Sender state that send will be blocked

[vchekan]

Documentation states that Sender::send will "block the current task until the send operation can proceed". The word "block" is potentially misleading, because it is usually applied as synonymous to "will block thread". Could it be reformulated with word "await" somehow? For example: "If the channel is full, this method will await until operation can proceed."

async-std/src/sync/channel.rs

Line 105 in fa91d7f

/// If the channel is full, this method will block the current task until the send operation