Update swift-syntax to 509.0.0

[pablocornejo]

The codebase is being updated to work with swift-syntax 509.0.0

[sidepelican]

LGTM, thank you!

[uhooi]

@rudro plz merge :)

[pablocornejo]

Hello @sidepelican @uhooi, is there something else required so that this can be merged?

[sidepelican]

We are already not maintainers and do not have the authority to merge.

According to #220, @rudro @alanzeino seems to be the maintainer, but I haven't seen much of them.

[alanzeino]

Sorry, I assumed you could still merge. Let me check the permissions.

[alanzeino]

@sidepelican can you show me what message you see on your end? I've double checked our branch protection rules and you should be able to merge as you have write permissions, along with @uhooi

The only thing I can't really tell is if Uber has an organization global protection rule that doesn't allow non–Uber employees to merge PRs. I'll have to get back to you on that. For now, I'll merge this.

In future if you at–mention me I can merge until we resolve this.

[uhooi]

@alanzeino The following message will be displayed:

You’re not authorized to merge this pull request.

[sidepelican]

Same.

[alanzeino]

Updated the Branch protection rule settings, should work now.

[uhooi]

@alanzeino thx!!
I can't select "Create a merge commit", can I just "Squash and merge"?

[alanzeino]

I also changed that; to match other projects at Uber.