🔨 Move branch `master` to `production`

It is more appropriate.

.gitlab-ci.yml

@@ -2,16 +2,16 @@ image: python:3.6-alpine
 
 publish:
   except:
-  - master
+  - production
   - devel
   script:
   - pip install -r requirements.txt
   - pelican -s pubconf-devel.py --fatal warnings
-  - pelican -s pubconf-master.py --fatal warnings
+  - pelican -s pubconf-production.py --fatal warnings
 
 pages:
   only:
-  - master
+  - production
   - devel
   script:
   - pip install -r requirements.txt