fix sleep method

Author: georgio

.travis.yml

@@ -2,13 +2,12 @@ sudo: false
 language: php
 
 php:
-  - 7.2
   - 7.3
   - 7.4
   - 8.0
 matrix:
     allow_failures:
-        - php: 8.0
+        - php: 7.2
 
 before_script:
   - composer self-update

composer.json

@@ -30,7 +30,7 @@
         ]
     },
     "require": {
-        "php": "^7.2 || 8.0.*"
+        "php": "^7.3 || 8.0.*"
     },
     "require-dev": {
         "ext-dom": "*",