Remove trailing whitespace in default /etc/selinux/config

See <https://pagure.io/atomic-wg/issue/341> - basically for libostree
(and hence rpm-ostree, and Fedora Editions that use it like Fedora Atomic Host),
the Anaconda `selinux --enforcing` verb will end up rewriting
`/etc/selinux/config` to the same value it had before.

But because of the trailing space character, this generates
a difference, and means the config file appears locally modified,
and hence deployed systems won't receive updates.

I think Anaconda should also be fixed to avoid touching the file *at all*
if it wouldn't result in a change, but let's remove the trailing space
here too, as it's better to fix in two places.

selinux-policy.spec

@@ -465,7 +465,7 @@ SELINUX=enforcing
 #     targeted - Targeted processes are protected,
 #     minimum - Modification of targeted policy. Only selected processes are protected. 
 #     mls - Multi Level Security protection.
-SELINUXTYPE=targeted 
+SELINUXTYPE=targeted
 
 " > /etc/selinux/config