Set the URL to one we control that is >65KB.

Some KDE mirrors have dropped KCalc 4.x, which makes this test flaky.
--- kio-5.116.0/autotests/favicontest.cpp.old	2024-05-04 11:40:29.000000000 +0000
+++ kio-5.116.0/autotests/favicontest.cpp	2025-08-10 05:32:25.751427228 +0000
@@ -216,7 +216,7 @@
 
     // Set icon URL to a >65KB file
     KIO::FavIconRequestJob *job = new KIO::FavIconRequestJob(url);
-    job->setIconUrl(QUrl("http://download.kde.org/Attic/4.13.2/src/kcalc-4.13.2.tar.xz"));
+    job->setIconUrl(QUrl("http://distfiles.adelielinux.org/source/adelie-kde-theme-1.0.tar.xz"));
     QVERIFY(willDownload(job));
     QVERIFY(!job->exec());
     QCOMPARE(job->error(), int(KIO::ERR_WORKER_DEFINED));