deps: axe-core@3.3.0

[patrickhulce]

Summary
Updates axe-core to version just released 2019-07-08.

Notable changes:

• API for synchronous run might be interesting for us to look into since IIRC there was a lot of time spent in async control passing we don't really need.
• Some big perf wins
• A few new rules we might want to add audits for (aria-input-field-label, aria-toggle-field-label)
• Lots of bug fixes

Related Issues/PRs
closes #9337, see dequelabs/axe-core#1597 (comment)

[brendankenny]

adds about 6KB after gzip :(

A few new rules we might want to add audits for (aria-input-field-label, aria-toggle-field-label)

do we need to disable any? (and maybe add them to #7127?)

looks like there's a smoke change needed, too

[patrickhulce]

done done and done.

yeah not sure what we can do about size other than put pressure on axe to trim some fat though :)

[brendankenny]

yeah not sure what we can do about size other than put pressure on axe to trim some fat though :)

no, not much. Custom axe bundling or something :)

[brendankenny]

LGTM!

[paulirish]

Some big perf wins

sgtm! on a test URL, i saw axe taking 1350ms before and now 1050ms. sweet

[connorjclark]

they suggest axe is twice as fast for large pages. hope that's true!