core.certmanager: Turn soft dependency on LuaSec into a hard
The default network backend server_epoll already requires LuaSec so
Prosody won't even start without it, so we can get rid of these lines
here too.
Thanks for your interest in contributing to the project!
There are many ways to contribute, such as helping improve the
documentation, reporting bugs, spreading the word or testing the latest
development version.
You can find more information on how to contribute at <https://prosody.im/doc/contributing>
See also the HACKERS and README files.