[Workflow] Fix Event constructor requirements
[Workflow] Fix Event constructor requirements

This has already been deprecied in 4.x
But while cleaning the 5.x branch, I forgot to apply this patch

See
https://github.com/symfony/symfony/pull/31824/files#diff-5f386ffb0109cc731bd98e63eea021b32faadd98791bd6ba65926d09c5e2ec40L37

symfony/workflow