Correct Safari support for background-clip

[lukewarlow]

Summary

This PR updates Safari support data for the background-clip property to show it's supported as of Safari 14.

Test results and supporting details

Based on issue it definitely wasn't supported before Safari 14. And definitely was from at least Safari 14.1.

I have verified it works on iOS 14.5 and Safari 15.2 personally.

Related issues

Fixes #13977

[lukewarlow]

I've looked but can't find any webkit commits to help confirm whether it was 14 or 14.1 that it was added in.

[ddbeck]

@queengooborg do you know if there's an easy way to test 14 versus 14.1?

If not, I'm OK with merging as-is.

[queengooborg]

SauceLabs has both versions available, that's the easiest way I can think of?

[ddbeck]

SauceLabs has both versions available, that's the easiest way I can think of?

@queengooborg wait, really? What combination of settings do I use to get that because it only showed me 14.1 when I checked (before asking for your input). If there's a trick to it, that would be great to know.

[queengooborg]

There's a little trick to it, yeah -- my apologies, I thought I wrote up how to do so but apparently not... Alas, I just found out this won't work for Safari 14 + 15, but I'll leave the trick here anyways:

In SauceLabs, when selecting Safari 10 through 13, the "OS Version" dropdown will include two different macOS versions. Simply select the older of the two, and you're good to go!

[ddbeck]

OK, since I can't directly test this to be sure it wasn't later, I'm going to merge it as written. Thank you, @lukewarlow! 🎉