Fixed unsound errors

[Lucretiel]

Currently, the zola error type has:

zola/components/errors/src/lib.rs

Lines 22 to 23 in 261a2ee

	unsafe impl Sync for Error {}
	unsafe impl Send for Error {}

These impls are unsound, because Box<dyn Error> may be a !Send or !Sync type, and because Syntect errors are !Sync. This pull request updates to Syntect 4.4, which fixes this, and updates source to be dyn Error + Send + Sync. This removes the unsoundness, and the need for any unsafe in error.

IMPORTANT: Please do not create a Pull Request adding a new feature without discussing it first.

The place to discuss new features is the forum: https://zola.discourse.group/
If you want to add a new feature, please open a thread there first in the feature requests section.

Sanity check:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Code changes

(Delete or ignore this section for documentation changes)

• Are you doing the PR on the next branch?

[Keats]

Thanks!