* en/book/ch05-repository-admin.xml
(svn.reposadmin.hooks.configuration): Tweak example to use string
substitution syntax, and call out that syntax in a <note>.
(svn.reposadmin.hooks.uses): Avoid introducing 'transaction
properties' as a standalone term. Mention backup/replication as
common uses. Drop (with a TODO left behind) the example of
ephemeral txnprop checking -- I can't even convince my*self* that
it's useful.