Replace single-quotes with double-quotes in a few SGML attributes.

Both are valid SGML, but let's be consistent.

Author: Peter Smith
Discussion: https://www.postgresql.org/message-id/CAHut%2BPtghjg0SBUTv%3D4Bpcy68d1zD3VAnZ3wX1DQSp39XKD9Sw%40mail.gmail.com

doc/src/sgml/ref/create_role.sgml

@@ -123,7 +123,7 @@ in sync when changing the above synopsis!
         These clauses determine whether a role will be permitted to
         create, alter, drop, comment on, and change the security label for
         other roles.
-        See <xref linkend='role-creation' /> for more details about what
+        See <xref linkend="role-creation"/> for more details about what
         capabilities are conferred by this privilege.
         If not specified, <literal>NOCREATEROLE</literal> is the default.
        </para>

doc/src/sgml/ref/createuser.sgml

@@ -48,7 +48,7 @@ PostgreSQL documentation
    Being a superuser implies the ability to bypass all access permission
    checks within the database, so superuser access should not be granted
    lightly. <literal>CREATEROLE</literal> also conveys
-   <link linkend='role-creation'>very extensive privileges</link>.
+   <link linkend="role-creation">very extensive privileges</link>.
   </para>
 
   <para>
@@ -254,7 +254,7 @@ PostgreSQL documentation
         The new user will be allowed to create, alter, drop, comment on,
         change the security label for other roles; that is,
         this user will have <literal>CREATEROLE</literal> privilege.
-        See <xref linkend='role-creation' /> for more details about what
+        See <xref linkend="role-creation"/> for more details about what
         capabilities are conferred by this privilege.
        </para>
       </listitem>

doc/src/sgml/ref/pgbench.sgml

@@ -1167,7 +1167,7 @@ pgbench <optional> <replaceable>options</replaceable> </optional> <replaceable>d
   </para>
 
   <variablelist>
-   <varlistentry id='pgbench-metacommand-gset'>
+   <varlistentry id="pgbench-metacommand-gset">
     <term>
      <literal>\gset [<replaceable>prefix</replaceable>]</literal>
      <literal>\aset [<replaceable>prefix</replaceable>]</literal>
@@ -1237,7 +1237,7 @@ SELECT 4 AS four \; SELECT 5 AS five \aset
     </listitem>
    </varlistentry>
 
-   <varlistentry id='pgbench-metacommand-set'>
+   <varlistentry id="pgbench-metacommand-set">
     <term>
      <literal>\set <replaceable>varname</replaceable> <replaceable>expression</replaceable></literal>
     </term>
@@ -1362,7 +1362,7 @@ SELECT 4 AS four \; SELECT 5 AS five \aset
     </listitem>
    </varlistentry>
 
-   <varlistentry id='pgbench-metacommand-pipeline'>
+   <varlistentry id="pgbench-metacommand-pipeline">
     <term><literal>\startpipeline</literal></term>
     <term><literal>\endpipeline</literal></term>