close old PRs

[staabm]

I guess the deployment of new PRs to a dev environment on plattform.sh doesnt work, because some old PRs occupy the available instances.

I remember @mnapoli mentioned there are 3 available slots.

see

[mnapoli]

I've closed one for now, I want to try #66 at some point because it seems like an interesting PR but it could break things in a very silent way, so it's hard to be confident :/

[staabm]

thx!

[staabm]

for the record: platformsh confirmed there are known problems with the github integration atm:
https://twitter.com/Crell/status/1040606744601341952