CI - drop php5.4 tests

It probably still works, but there is nikic/php-parser requirements hell...
https://github.com/EdgedesignCZ/phpqa/actions/runs/19562416916/job/56017194355?pr=270#step:5:44
https://github.com/EdgedesignCZ/phpqa/actions/runs/19562566742/job/56017623098?pr=270#step:5:41

Author: zdenekdrahos

.github/workflows/php.yml

@@ -15,7 +15,6 @@ jobs:
         php: [5.5]
         include:    
           # PHP5
-          - { php: 5.4, areSuggestedToolsInstalled: yes }
           - { php: 5.6, areSuggestedToolsInstalled: yes, allowedSecurityErrors: 1 }
           # PHP7
           - { php: 7.0 }