Remove incorrect statement about IPC configuration on OpenBSD

kern.ipc.shm_use_phys is not a sysctl on OpenBSD, and SEMMAP is not
a kernel configuration option. These were probably copy pasteos from
when the documentation had a single paragraph for *BSD.

Author: Daniel Gustafsson <daniel@yesql.se>

Author: mhagander

doc/src/sgml/runtime.sgml

@@ -959,16 +959,9 @@ option        SYSVSEM
 option        SEMMNI=256
 option        SEMMNS=512
 option        SEMMNU=256
-option        SEMMAP=256
 </programlisting>
        </para>
 
-       <para>
-        You might also want to configure your kernel to lock shared
-        memory into RAM and prevent it from being paged out to swap.
-        This can be accomplished using the <command>sysctl</command>
-        setting <literal>kern.ipc.shm_use_phys</literal>.
-       </para>
       </listitem>
      </varlistentry>