The status of P1353R0 was "Partial" because we don't define the
__cpp_lib_three_way_comparison macro, but that's because we don't
support the feature. So the paper can be marked as done.

	* doc/xml/manual/status_cxx2020.xml: Add feature-test macro for
	P0811R3. Change status of P1353R0.
	* doc/html/*: Regenerate.

Committed to trunk.