munin-node-configure: remove "--exitnoterror" argument

Since commit 37e72a5 plugins are not expected to return with a
non-zero exit code during autoconf anymore.

The deprecation of a non-zero exitcode for autoconf dates back at least
to commit 71280a8 (2009) or earlier.

Closes: #1341

Thanks, kboenke!

node/sbin/munin-node-configure

@@ -501,10 +501,6 @@ Override plugin configuration directory [@@CONFDIR@@/plugin-conf.d/]
 
 Override plugin library [@@LIBDIR@@/plugins/]
 
-=item B<< --exitnoterror >>
-
-Do not consider plugins that exit non-zero exit-value as error.
-
 =item B<< --suggest >>
 
 Suggest plugins that might be added or removed, instead of those that are