Update travis config to php 7.2 and 7.3. Minor config improvements

Author: Willem Wigman

.travis.yml

@@ -1,4 +1,4 @@
-sudo: required
+os: linux
 dist: trusty
 group: edge
 addons:
@@ -11,21 +11,21 @@ addons:
   hosts:
     - magento2.travis
 language: php
-matrix:
+jobs:
   include:
-    - php: 7.2
+    - php: 7.3
       env:
         - MAGENTO_VERSION=2.3
         - TEST_SUITE=integration
-    - php: 7.2
+    - php: 7.3
       env:
         - MAGENTO_VERSION=2.4-develop
         - TEST_SUITE=integration
-    - php: 7.1
+    - php: 7.2
       env:
         - MAGENTO_VERSION=2.3
         - TEST_SUITE=integration
-    - php: 7.1
+    - php: 7.2
       env:
         - MAGENTO_VERSION=2.4-develop
         - TEST_SUITE=integration