doc: Get rid of unnecessary space character from some index items.

Previously some index items have " ," (i.e., space + comma) in the docs
as follows. Since the space character before the comma is unnecessary,
this commit gets rid of that for the sake of consistency with other
index items.

   parallel_leader_participation configuration parameter , Other Planner Options

Author: Fujii Masao
Reviewed-by: Euler Taveira
Discussion: https://postgr.es/m/e87b4ddf-1498-2850-bf55-519df3928fd4@oss.nttdata.com

Author: MasaoFujii

doc/src/sgml/config.sgml

@@ -5650,10 +5650,7 @@ SELECT * FROM parent WHERE key = 2400;
       <term>
        <varname>parallel_leader_participation</varname> (<type>boolean</type>)
        <indexterm>
-        <primary>
-         <varname>parallel_leader_participation</varname> configuration
-         parameter
-        </primary>
+        <primary><varname>parallel_leader_participation</varname> configuration parameter</primary>
        </indexterm>
       </term>
       <listitem>

doc/src/sgml/pgtrgm.sgml

@@ -377,9 +377,7 @@
     <term>
      <varname>pg_trgm.word_similarity_threshold</varname> (<type>real</type>)
      <indexterm>
-      <primary>
-       <varname>pg_trgm.word_similarity_threshold</varname> configuration parameter
-      </primary>
+      <primary><varname>pg_trgm.word_similarity_threshold</varname> configuration parameter</primary>
      </indexterm>
     </term>
     <listitem>
@@ -394,9 +392,7 @@
     <term>
      <varname>pg_trgm.strict_word_similarity_threshold</varname> (<type>real</type>)
      <indexterm>
-      <primary>
-       <varname>pg_trgm.strict_word_similarity_threshold</varname> configuration parameter
-      </primary>
+      <primary><varname>pg_trgm.strict_word_similarity_threshold</varname> configuration parameter</primary>
      </indexterm>
     </term>
     <listitem>