pgsql: Fix warnings in man page build

Fix warnings in man page build

The changes in the CREATE POLICY man page from commit
87c2a17fee784c7e1004ba3d3c5d8147da676783 triggered a stylesheet bug that
created some warning messages and incorrect output. This installs a
workaround.

Also improve the whitespace a bit so it looks better.

Branch
------
REL9_5_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/353dd75260e00379240be6a7b8897e90449a95db

Modified Files
--------------
doc/src/sgml/ref/create_policy.sgml | 9 +++------
doc/src/sgml/stylesheet-man.xsl | 6 ++++++
2 files changed, 9 insertions(+), 6 deletions(-)