Update versions.json

Author: fabpot

.github/versions.json

@@ -1,10 +1,10 @@
 {
     "lts": "5.4",
-    "stable": "6.2",
-    "next": "6.3",
-    "previous": "6.1",
-    "dev": "6.3",
-    "dev-name": "6.3",
+    "stable": "6.3",
+    "next": "6.4",
+    "previous": "6.2",
+    "dev": "6.4",
+    "dev-name": "6.4",
     "splits": {
         "symfony/all-my-sms-notifier": [
             "5.3",