fix(swarm): improve error message on false DialPeerCondition

[mxinden]

With PeerCondition::Disconnected, dialing an already connected peer results in the following error message:

Dial error: condition Disconnected for dialing peer was false

This is not intuitive for newcomers. Something along the lines of the below would be more intuitive:

Dial error: condition dial was configured to only happen when disconnected (`PeerCondition::Disconnected`), but node is already connected, thus cancelling new dial.

rust-libp2p/swarm/src/lib.rs

Lines 1583 to 1585 in e36e8ce

	DialError::DialPeerConditionFalse(c) => {
	write!(f, "Dial error: condition {c:?} for dialing peer was false.")
	}

See e.g. confusion by user #4395