Doc: manually break lines in wide UUID examples.

Doc: manually break lines in wide UUID examples.

Buildfarm member crake has been complaining "WARNING: The contents of
fo:inline line 1 exceed the available area in the inline-progression
direction by 20500 millipoints. (See position 23808:106)" since
ba57dcfdc went in.  The other doc-building animals are not showing
this warning, and I don't see it on my RHEL8 workstation either, but
I was able to reproduce it on a Fedora 41 box.  So apparently this
is due to a recent-ish change in DocBook's line-breaking heuristics,
which caused it to cope less well with the UUIDs in these examples.
Put in some zero-width spaces to encourage the PDF toolchain to
break these lines in a better place.  (Only one of these examples
actually needs this today, but I marked up all three to ensure that
they get wrapped in a consistent way.)