doc: Fix description of some GUCs in docs and postgresql.conf.sample

The following parameters have been imprecise, or incorrect, about their
description (PGC_POSTMASTER or PGC_SIGHUP):
- autovacuum_work_mem (docs, as of 9.6~)
- huge_page_size (docs, as of 14~)
- max_logical_replication_workers (docs, as of 10~)
- max_sync_workers_per_subscription (docs, as of 10~)
- min_dynamic_shared_memory (docs, as of 14~)
- recovery_init_sync_method (postgresql.conf.sample, as of 14~)
- remove_temp_files_after_crash (docs, as of 14~)
- restart_after_crash (docs, as of 9.6~)
- ssl_min_protocol_version (docs, as of 12~)
- ssl_max_protocol_version (docs, as of 12~)

This commit adjusts the description of all these parameters to be more
consistent with the practice used for the others.

Revewed-by: Justin Pryzby
Discussion: https://postgr.es/m/YK2ltuLpe+FbRXzA@paquier.xyz
Backpatch-through: 9.6

doc/src/sgml/config.sgml

@@ -1633,6 +1633,9 @@ include_dir 'conf.d'
         the value of <xref linkend="guc-maintenance-work-mem"/> should
         be used instead.  The setting has no effect on the behavior of
         <command>VACUUM</command> when run in other contexts.
+        This parameter can only be set in the
+        <filename>postgresql.conf</filename> file or on the server command
+        line.
        </para>
       </listitem>
      </varlistentry>
@@ -3692,7 +3695,8 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
         <varname>max_worker_processes</varname>.
        </para>
        <para>
-        The default value is 4.
+        The default value is 4. This parameter can only be set at server
+        start.
        </para>
       </listitem>
      </varlistentry>
@@ -3717,7 +3721,9 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
         <varname>max_logical_replication_workers</varname>.
        </para>
        <para>
-        The default value is 2.
+        The default value is 2. This parameter can only be set in the
+        <filename>postgresql.conf</filename> file or on the server command
+        line.
        </para>
       </listitem>
      </varlistentry>
@@ -8261,6 +8267,11 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
         useful to disable the restart so that the clusterware can gain
         control and take any actions it deems appropriate.
        </para>
+
+       <para>
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
+       </para>
       </listitem>
      </varlistentry>