sitesmith cleaner: drop images.pexels.com from the AI image host allow-list

Stock photos are imported into the site's assets, never hotlinked, so the
only external image host model output may use is placehold.co.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0185ukXgk6UunFCKyXqLe2Cq

craft/scripts/e2e-sitesmith-cleaned.mjs

@@ -28,7 +28,7 @@ fs.rmSync(tmp, { force: true });
 
 const SITE = 'http://site.test';
 // The published page's own head resources (fonts, Font Awesome) + the cleaner's image hosts.
-const ALLOWED_HOSTS = new Set(['site.test', 'fonts.googleapis.com', 'fonts.gstatic.com', 'cdnjs.cloudflare.com', 'images.pexels.com', 'placehold.co']);
+const ALLOWED_HOSTS = new Set(['site.test', 'fonts.googleapis.com', 'fonts.gstatic.com', 'cdnjs.cloudflare.com', 'placehold.co']);
 const PNG = Buffer.from('iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg==', 'base64');
 
 let pass = 0; let fail = 0;