Allow v3 contracts where possible

Author: derrabus

Service/composer.json

@@ -18,7 +18,7 @@
     "require": {
         "php": ">=7.2.5",
         "psr/container": "^1.1",
-        "symfony/deprecation-contracts": "^2.1"
+        "symfony/deprecation-contracts": "^2.1|^3"
     },
     "conflict": {
         "ext-psr": "<1.1|>=2"