[Freeze Break Request: ] Upgrade pagure.io to pagure 5.1.3

[Pierre-Yves Chibon]

Good Morning Everyone,

We managed yesterday and today to fixes a couple of not hard but annoying little
bugs in pagure. They lead to the release 5.1.3 with the following changelog:

5.1.3 (2018-10-11)
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- Don't sync up ssh keys if there are already some
- Do not notify twice when pushing commits to an open PR
- Update git-multimail to the 1.4.0 version (fixes getting it working with py3)


I've pushed 5.1.3 to staging and after giving some more testing tomorrow I was
thinking about pushing it to prod if people thinks it's a good idea.

So, what do you think? :)


Pierre