doc PG relnotes: remove warning about commit links in PDF build

Make paragraph empty instead of removing it.

Discussion: https://postgr.es/m/[email protected]

Backpatch-through: 12

Author: bmomjian

doc/src/sgml/stylesheet-fo.xsl

@@ -18,11 +18,11 @@
 
 <!--
 Suppress the description of the commit link markers in print mode.
-Caues an "Unresolved ID reference found" warning during PDF builds
-because the paragraph is suppressed in the output.
+Use "node()" to keep the paragraph but remove all content;  prevents
+an "Unresolved ID reference found" warning during PDF builds.
 -->
-<xsl:template match="appendix[@id='release']//para[@id='release-commit-links']">
-  <!-- Output nothing for this para -->
+<xsl:template match="appendix[@id='release']//para[@id='release-commit-links']//node()">
+  <!-- Output an empty para -->
 </xsl:template>
 
 <xsl:param name="use.extensions" select="1"></xsl:param>