Use older mysql

.travis.yml

@@ -4,13 +4,8 @@ sudo: required
 php:
     - '7.2'
     - nightly
-addons:
-  apt:
-    sources:
-        - mysql-5.7-trusty
-    packages:
-        - mysql-server
-        - mysql-client
+services:
+    - mysql
 before_script:
     - sudo mysql -e "use mysql; update user set authentication_string=PASSWORD('new_password') where User='root'; update user set plugin='mysql_native_password';FLUSH PRIVILEGES;"
     - sudo mysql_upgrade