*/*: switch dependency from devel/py-lxml5 to devel/py-lxml

Currently, there are two versions of python XML processing library
which conflict each other in the ports tree, namely:

• devel/py-lxml5 (now at version 5.4.0)
• devel/py-lxml (now at version 6.0.1)

To avoid the situation that some ports depend on py-lxml5 and some
others do on py-lxml (by switching dependencies individually), this
commit switches the dependencies from py-lxml5 to py-lxml at once.

Additional note: There are still two ports (textproc/py-rdflib and
www/py-draftjs-exporter) depending on py-lxml5 since they limit upper
version to less than 6.

PR: 289491
Approved by: Michiel van Baak Jansen <michiel@vanbaak.eu>, arrowd,

		crees, madpilot, delphij, marcus, nivit, kai,
		skreuzer, fluffy, bofh, thierry, stephen, sunpoet,
		0mp, Eric Camachat <eric@camachat.org>