Revert "Reformat commit 6b2a1445ec8a631060c4cbff3f172bf31d3379b9"

This reverts commit 6ba56f0805b549b001e3149d6a7fba04e970d2dc.
We should instead patch up the following paragraph (the one about
pg_relation_size) so that it doesn't have cross-references that
break across lines in PDF output.)
Rearrange documentation paragraph describing pg_relation_size().

Break the list of available options into an <itemizedlist> instead of
inline sentences.  This is mostly motivated by wanting to ensure that the
cross-references to the FSM and VM docs don't cross page boundaries in PDF
format; but it seems to me to read more easily this way anyway.  I took the
liberty of editorializing a bit further while at it.

Per complaint from Magnus about 9.0.18 docs not building in A4 format.
Patch all active branches so we don't get blind-sided by this particular
issue again in future.