Merge 2 stages

.travis.yml

@@ -44,11 +44,11 @@ jobs:
   #allow_failures:
   #- php: nightly
   include:
-    - stage: PHP 5.6
+    - stage: PHP 5.6-7.4
       if: type = push
       php: '5.6'
       env: DB=postgresql
-    - stage: PHP 7.4
+    - stage: PHP 5.6-7.4
       if: type = pull_request OR type = push
       php: '7.4'
       env: DB=mysql