pgsql: Fix docs build for website styles

Fix docs build for website styles

Building the docs with STYLE=website referenced a stylesheet that long
longer exists on the website, since we changed it to use versioned
references.

To make it less likely for this to happen again, point to a single
stylesheet on the website which will in turn import the required one.
That puts the process entirely within the scope of the website
repository, so next time a version is switched that's the only place
changes have to be made, making them less likely to be missed.

Per (off-list) discussion with Peter Geoghegan and Jonathan Katz.

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/186f6168b73de6472e8aeb6e96b2ec6c73fd7b89

Modified Files
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doc/src/sgml/stylesheet.xsl | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)