Fixes a compiler error when swift 6's strict concurrency checking is enabled

[tritchey]

The concurrency checking doesn't like the validationProvider in TokenSystemValidator. After fixing the concurrency complaint, it looks like the tokenValidator isn't being strongly held any more, so a new tokenValidator property was added to TextSystemStyler.

[mattmassicotte]

Wow this is an interesting find! This project has a tendency to turn up compiler bugs - I have found many while working on it. In this case, it looks like a regression in 6.2, though possibly also 6.1, unsure exactly.

I've been looking more closely, as making this return value weak is a fairly significant semantic change. I discovered a more-minimally-invasive change that seems to also work. What do you think?

An explicit, non-weak self capture in the second argument:

	var validationProvider: HybridSyncAsyncValueProvider<Validator.ContentRange, Validation, Never> {
		.init(
			syncValue: { self.validate($0) },
			asyncValue: { [self] _, range in await self.validate(range) }
		)
	}

[tritchey]

Hi Matt,
Oh, yeah - I'm brand-new looking at the code base so wasn't sure what the implications might be. I tested you version an it is working great, so a much more straightforward fix.

[mattmassicotte]

I think this is just CI being poorly configured. I'll have a look that.

Thanks so much for taking the time to let me know about this and fix it. I really appreciate it!