Fix XML id to match GUC name

For some reason, the id of the description of max_parallel_maintenance_workers has been guc-max-parallel-workers-maintenance since the beginning. Flip that around to make it consistent.

Author: petere

doc/src/sgml/config.sgml

@@ -2367,7 +2367,7 @@ include_dir 'conf.d'
  <para>
  When changing this value, consider also adjusting
  <xref linkend="guc-max-parallel-workers"/>,
- <xref linkend="guc-max-parallel-workers-maintenance"/>, and
+ <xref linkend="guc-max-parallel-maintenance-workers"/>, and
  <xref linkend="guc-max-parallel-workers-per-gather"/>.
  </para>
  </listitem>
@@ -2415,7 +2415,7 @@ include_dir 'conf.d'
  </listitem>
  </varlistentry>
 
- <varlistentry id="guc-max-parallel-workers-maintenance" xreflabel="max_parallel_maintenance_workers">
+ <varlistentry id="guc-max-parallel-maintenance-workers" xreflabel="max_parallel_maintenance_workers">
  <term><varname>max_parallel_maintenance_workers</varname> (<type>integer</type>)
  <indexterm>
  <primary><varname>max_parallel_maintenance_workers</varname> configuration parameter</primary>
@@ -2464,7 +2464,7 @@ include_dir 'conf.d'
  Sets the maximum number of workers that the system can support for
  parallel operations. The default value is 8. When increasing or
  decreasing this value, consider also adjusting
- <xref linkend="guc-max-parallel-workers-maintenance"/> and
+ <xref linkend="guc-max-parallel-maintenance-workers"/> and
  <xref linkend="guc-max-parallel-workers-per-gather"/>.
  Also, note that a setting for this value which is higher than
  <xref linkend="guc-max-worker-processes"/> will have no effect,

doc/src/sgml/ref/create_index.sgml

@@ -771,7 +771,7 @@ Indexes:
  least a <literal>32MB</literal> share of the total
  <varname>maintenance_work_mem</varname> budget. There must also be
  a remaining <literal>32MB</literal> share for the leader process.
- Increasing <xref linkend="guc-max-parallel-workers-maintenance"/>
+ Increasing <xref linkend="guc-max-parallel-maintenance-workers"/>
  may allow more workers to be used, which will reduce the time
  needed for index creation, so long as the index build is not
  already I/O bound. Of course, there should also be sufficient

doc/src/sgml/ref/vacuum.sgml

@@ -239,7 +239,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
  (without <literal>FULL</literal>), if the <literal>PARALLEL</literal> option
  is omitted, then the number of workers is determined based on the number of
  indexes on the relation that support parallel vacuum operation and is further
- limited by <xref linkend="guc-max-parallel-workers-maintenance"/>. An index
+ limited by <xref linkend="guc-max-parallel-maintenance-workers"/>. An index
  can participate in parallel vacuum if and only if the size of the index is
  more than <xref linkend="guc-min-parallel-index-scan-size"/>. Please note
  that it is not guaranteed that the number of parallel workers specified in