pgsql: doc: Fix titles of some pg_buffercache functions.

doc: Fix titles of some pg_buffercache functions.

As in commit 59d6c03956, use <function> rather than <structname> in
the <title> to be consistent with how other functions in this
module are documented.

Oversights in commits dcf7e1697b and 9ccc049dfe.

Author: Noboru Saito <noborusai@gmail.com>
Discussion: https://postgr.es/m/CAAM3qn%2B7KraFkCyoJCHq6m%3DurxcoHPEPryuyYeg%3DQ0EjJxjdTA%40mail.gmail.com
Backpatch-through: 18

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b237f5422bc0667754f986f9d5bfc34a13401bc1

Modified Files
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doc/src/sgml/pgbuffercache.sgml | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)