Switch build from createrepo-c to createrepo

[HebaruSan]

Problem

After #3605, the build failed:

Cause

Ubuntu and Debian have createrepo-c for generating RPM repos. I hoped that mono:latest would be the same 🤞, but it was not to be.

$ docker run -it --entrypoint sh mono:latest

# apt-cache search createrepo
createrepo - tool to generate the metadata for a yum repository

Changes

• The deploy.yml file is updated to install createrepo instead of createrepo-c
• The RPM Makefile now uses createrepo if you have it, or createrepo_c if you don't, so local dev will still work

I'll merge this shortly.

[HebaruSan]

That worked, but the nightly repo only has ckan-1.31.1-1.noarch, which lacks a daily incrementing version number part, so all the builds until the next release will share the same version number and RPM won't update them...

[HebaruSan]

Updated release.yml in 5917e37.