Reconfigure deprecation helper to not fail builds

This configures the deprecation helper to not fail builds on all Symfony versions except the latest stable one. We always expect no deprecations when running against the latest versions of Symfony.

.travis.yml

@@ -31,30 +31,30 @@ jobs:
   include:
     # Tests the lowest set of depedencies
     - php: 7.1
-      env: deps=low SYMFONY_DEPRECATIONS_HELPER=weak
+      env: deps=low SYMFONY_DEPRECATIONS_HELPER=999999
       install:
         - COMPOSER_MEMORY_LIMIT=-1 travis_retry composer update -n --prefer-lowest --prefer-stable --prefer-dist
 
     # Test against latest Symfony 3.4 stable
     - php: 7.1
-      env: SYMFONY_VERSION="3.4.*"
+      env: SYMFONY_VERSION="3.4.*" SYMFONY_DEPRECATIONS_HELPER=999999
 
     # Test against latest Symfony 3.4 dev version
     - php: 7.1
-      env: stability=dev SYMFONY_DEPRECATIONS_HELPER=weak SYMFONY_VERSION="3.4.*"
+      env: stability=dev SYMFONY_DEPRECATIONS_HELPER=999999 SYMFONY_VERSION="3.4.*"
       install:
         - travis_retry composer update -n --prefer-dist
 
     # Test against latest Symfony 4.1 dev version
     - php: 7.1
-      env: stability=dev SYMFONY_DEPRECATIONS_HELPER=weak SYMFONY_VERSION="4.1.*"
+      env: stability=dev SYMFONY_DEPRECATIONS_HELPER=999999 SYMFONY_VERSION="4.1.*"
       install:
         - composer require --dev "symfony/messenger:4.1.*" --no-update
         - travis_retry composer update -n --prefer-dist
 
     # Test against latest Symfony 4.2 dev version
     - php: 7.1
-      env: stability=dev SYMFONY_DEPRECATIONS_HELPER=weak SYMFONY_VERSION="4.2.*"
+      env: stability=dev SYMFONY_DEPRECATIONS_HELPER=999999 SYMFONY_VERSION="4.2.*"
       install:
         - composer require --dev "symfony/messenger:4.2.*" --no-update
         - travis_retry composer update -n --prefer-dist