upgrade to laravel 7 and set branch to v2

vendor/symfony/routing/CompiledRoute.php

@@ -64,12 +64,9 @@ class CompiledRoute implements \Serializable
     }
 
     /**
-     * @return string
-     *
-     * @internal since Symfony 4.3
-     * @final since Symfony 4.3
+     * @internal
      */
-    public function serialize()
+    final public function serialize(): string
     {
         return serialize($this->__serialize());
     }
@@ -87,10 +84,9 @@ class CompiledRoute implements \Serializable
     }
 
     /**
-     * @internal since Symfony 4.3
-     * @final since Symfony 4.3
+     * @internal
      */
-    public function unserialize($serialized)
+    final public function unserialize($serialized)
     {
         $this->__unserialize(unserialize($serialized, ['allowed_classes' => false]));
     }