Update versions.json

Author: nicolas-grekas

.github/versions.json

@@ -668,20 +668,6 @@
             "5.4",
             "6.0"
         ],
-        "symfony/phpunit-bridge": [
-            "3.4",
-            "4.0",
-            "4.1",
-            "4.2",
-            "4.3",
-            "4.4",
-            "5.0",
-            "5.1",
-            "5.2",
-            "5.3",
-            "5.4",
-            "6.0"
-        ],
         "symfony/postmark-mailer": [
             "4.3",
             "4.4",