Mk/bsd.port.mk: mark FreeBSD 13.4 as unsupported.
all: drop compatibility for FreeBSD 13.4 from jbeich's ports
audio/ardour: remove detections for end-of-life 13.4, 14.0, and 14.1
lang/crystal: remove support for FreeBSD twelve and earlier
net/udt: simplify a tautology