Remove errant </div> from README

There was a stray closing div tag in the README that caused a
rendering failure on the forge.puppetlabs.com module page. Removing
that tag should be meaningless for the REAMDE and correct the bug
on Forge.

Thanks for publishing your module to the Forge! Sorry for the trouble. Once you release a version with this patch, the module page should look as we intend it. For the future, we'll also update the Forge to not bug out when we get an errant tag like this.