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
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/d21ddc220fc735da84c9fa7bae1968f6953a6c8c

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