Remove 3.4 (EOL)

See https://www.redmine.org/news/128:

> Please note that Redmine 3.x has reached end of life, not supported any longer and (as well) vulnerable to these security issues. You should upgrade to Redmine 4 to get security updates.

Author: tianon

.travis.yml

@@ -6,8 +6,6 @@ env:
   - VERSION=4.1/alpine
   - VERSION=4.0
   - VERSION=4.0/alpine
-  - VERSION=3.4
-  - VERSION=3.4/alpine
 
 install:
   - git clone https://github.com/docker-library/official-images.git ~/official-images