use flock in default as it works out of the box (#1142)

symfony/lock/4.4/manifest.json

@@ -5,6 +5,6 @@
     "env": {
         "#1": "Choose one of the stores below",
         "#2": "LOCK_DSN=redis://localhost",
-        "LOCK_DSN": "semaphore"
+        "LOCK_DSN": "flock"
     }
 }

symfony/lock/5.2/manifest.json

@@ -5,6 +5,6 @@
     "env": {
         "#1": "Choose one of the stores below",
         "#2": "postgresql+advisory://db_user:db_password@localhost/db_name",
-        "LOCK_DSN": "semaphore"
+        "LOCK_DSN": "flock"
     }
 }