Build/Test Tools: Update actions within test workflows to the latest versions.

This updates two published GitHub actions to their latest versions:

- `actions/setup-node` from `v1` to `v2`.
- `styfle/cancel-workflow-action` from `0.5.0` to `0.8.0`.

See #50401.
Built from https://develop.svn.wordpress.org/trunk@50387


git-svn-id: http://core.svn.wordpress.org/trunk@49998 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-beta3-50386';
+$wp_version = '5.7-beta3-50387';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.