[Website] Switch the CORS Proxy URL to wordpress-playground-cors-proxy.net

[adamziel]

Updates playground.wordpress.net to use the new CORS Proxy URL. This makes sure the requests are not routed through
https://playground.wordpress.net/cors-proxy.php anymore.

As a next step, we should restrict the access from playground.wordpress.net

Testing instructions

None, this is a production-only change. Merge, deploy, confirm it worked.

cc @brandonpayton

[brandonpayton]

Thank you. ☺️ I was just thinking we'd need to do this.

[brandonpayton]

Let's do this.

[brandonpayton]

I used the test URL from PR #1926:

https://playground.wordpress.net/?php=8.0&wp=6.6&networking=yes&language=&multisite=no&random=f1qv1twpssr#%7B%22landingPage%22:%22/network-test.php%22,%22preferredVersions%22:%7B%22php%22:%228.0%22,%22wp%22:%22latest%22%7D,%22phpExtensionBundles%22:%5B%22kitchen-sink%22%5D,%22steps%22:%5B%7B%22step%22:%22writeFile%22,%22path%22:%22/wordpress/network-test.php%22,%22data%22:%22%3C?php%20echo%20'Hello-dolly.zip%20downloaded%20from%20https://downloads.wordpress.org/plugin/hello-dolly.1.7.3.zip%20has%20this%20many%20bytes:%20';%20var_dump(strlen(file_get_contents('https://downloads.wordpress.org/plugin/hello-dolly.1.7.3.zip')));%22%7D%5D%7D 

And the result was:

Hello-dolly.zip downloaded from https://downloads.wordpress.org/plugin/hello-dolly.1.7.3.zip has this many bytes: int(1887) 

And the dev tools Networking tab shows a request to https://wordpress-playground-cors-proxy.net/?https://downloads.wordpress.org/plugin/hello-dolly.1.7.3.zip.

Looks like we're in the clear, @adamziel!

[adamziel]

Lovely!