Doc: correct spelling of meson switch.

It's --auto-features not --auto_features.

Reported-by: Egor Chindyaskin <kyzevan23@mail.ru>
Discussion: https://postgr.es/m/172465652540.862882.17808523044292761256@wrigleys.postgresql.org
Discussion: https://postgr.es/m/1979661.1746212726@sss.pgh.pa.us
Backpatch-through: 16

doc/src/sgml/installation.sgml

@@ -2725,7 +2725,7 @@ ninja install
 
     <variablelist>
      <varlistentry id="configure-auto-features-meson">
-      <term><option>--auto_features={ auto | enabled | disabled }</option></term>
+      <term><option>--auto-features={ auto | enabled | disabled }</option></term>
       <listitem>
        <para>
         Setting this option allows you to override the value of all