Update .travis.yml

Author: vigneshgurusamy

.travis.yml

@@ -1,20 +1,21 @@
 language: php
 
-sudo: false
+os: linux
+dist: bonic
 
 php:
-    - 7.4
+  - 7.4
 
 cache:
   directories:
     - $HOME/.composer/cache
 
 before_script:
-    - travis_retry composer self-update
-    - travis_retry composer update --no-interaction
+  - travis_retry composer self-update
+  - travis_retry composer update --no-interaction
 
 script:
-    - vendor/bin/phpunit --coverage-clover=coverage.xml
+  - vendor/bin/phpunit --coverage-clover=coverage.xml
 
 after_success:
-    - bash <(curl -s https://codecov.io/bash)
+  - bash <(curl -s https://codecov.io/bash)