doc: clarify DROP EXTENSION dependent members text

Member tracking was added in PG 13.

Reported-by: David G. Johnston

Discussion: https://postgr.es/m/CAKFQuwY1YtxQHVWUFYvSnOjZ5VPpXjF33V52bSKEwFjK2K=1Aw@mail.gmail.com

Author: David G. Johnston

Backpatch-through: 13

Author: bmomjian

doc/src/sgml/ref/drop_extension.sgml

@@ -30,7 +30,7 @@ DROP EXTENSION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> [
 
   <para>
    <command>DROP EXTENSION</command> removes extensions from the database.
-   Dropping an extension causes its component objects, and other explicitly
+   Dropping an extension causes its member objects, and other explicitly
    dependent routines (see <xref linkend="sql-alterroutine"/>,
    the depends on extension action), to be dropped as well.
   </para>
@@ -79,9 +79,9 @@ DROP EXTENSION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> [
     <term><literal>RESTRICT</literal></term>
     <listitem>
      <para>
-      This option prevents the specified extensions from being dropped
-      if there exists non-extension-member objects that depends on any
-      the extensions.  This is the default.
+      This option prevents the specified extensions from being dropped if
+      other objects, besides these extensions, their members, and their
+      explicitly dependent routines, depend on them.  This is the default.
      </para>
     </listitem>
    </varlistentry>