minor #20907 [Uid] Fix Uuid::v8() usage example to show it requires a UUID string (Hmache)

This PR was submitted for the 7.3 branch but it was merged into the 6.4 branch instead.

Discussion
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[Uid] Fix Uuid::v8() usage example to show it requires a UUID string

This update corrects the usage example of Uuid::v8() to prevent misuse and confusion

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Commits
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3abba12 [uid] Fix Uuid::v8() usage example to show it requires a UUID string

Author: javiereguiluz

components/uid.rst

@@ -140,7 +140,7 @@ of the UUID value is specific to each implementation and no format should be ass
     use Symfony\Component\Uid\Uuid;
 
     // $uuid is an instance of Symfony\Component\Uid\UuidV8
-    $uuid = Uuid::v8();
+    $uuid = Uuid::v8('d9e7a184-5d5b-11ea-a62a-3499710062d0');
 
 .. versionadded:: 6.2