doc: Don't reference /etc/modprobe.conf

kmod doesn't read /etc/modprobe.conf at all, so don't mention it in the
modprobe man page.  Point users to modprobe.d(5) instead.
diff --git a/man/modprobe.xml b/man/modprobe.xml
index e98e44e..0e101a8 100644
--- a/man/modprobe.xml
+++ b/man/modprobe.xml
@@ -80,10 +80,10 @@
       <command>modprobe</command> looks in the module directory
       <filename>/lib/modules/`uname -r`</filename> for all
       the modules and other files, except for the optional
-      <filename>/etc/modprobe.conf</filename> configuration file and
+      configuration files in the
       <filename>/etc/modprobe.d</filename> directory
       (see <citerefentry>
-        <refentrytitle>modprobe.conf</refentrytitle><manvolnum>5</manvolnum>
+        <refentrytitle>modprobe.d</refentrytitle><manvolnum>5</manvolnum>
       </citerefentry>). <command>modprobe</command> will also use module
       options specified on the kernel command line in the form of
       &lt;module&gt;.&lt;option&gt; and blacklists in the form of