Tests: Add comment to explain when e2e test for gutenberg is skipped

Follow-up to [58046].

Reviewed by jorbin.
Merges [58141] to the 6.4 branch.

See #60971.

git-svn-id: https://develop.svn.wordpress.org/branches/6.4@58154 602fd350-edb4-49c9-b593-d223f7449a82

Author: ockham

tests/e2e/specs/gutenberg-plugin.test.js

@@ -29,6 +29,7 @@ test.describe( 'Gutenberg plugin', () => {
 
 		expect( plugin.status ).toBe( 'inactive' );
 
+		// Only run this test on versions of WordPress that are still supported by the Gutenberg Plugin
 		try {
 			await requestUtils.activatePlugin( 'gutenberg' );
 		} catch ( error ) {