Various updates

• Remove deprecated template: https://gitlab.com/gitlab-org/gitlab/-/issues/439157
• Remove support for PHP 5.6

plugins/templates/matrix-redis.yml

-PHPunit:PHP5.6:MySQL:Redis:
-  stage: test
-  image: containers.ethitter.com:443/docker/images/php:5.6
-  services:
-    - mysql:5.6
-    - redis:alpine
-  script:
-    - find . -type "f" -iname "*.php" | xargs -L "1" php -l
-    - phpunit
-
 PHPunit:PHP7.0:MySQL:Redis:
   stage: test
   image: containers.ethitter.com:443/docker/images/php:7.0