Set YourKit update site to 2026.3

Fixes: #3845

Author: trancexpress

releng/org.eclipse.ui.releng/platformUiTools.p2f

@@ -119,7 +119,7 @@
     </iu>
     <iu id='com.yourkit.profiler.feature.group' name='Yourkit' version='0.0.0'>
         <repositories size='1'>
-            <repository location='https://www.yourkit.com/download/yjp2025_9_for_eclipse/'/>
+            <repository location='https://www.yourkit.com/dl/eclipse/2026.3/'/>
         </repositories>
     </iu>
     <iu id='com.microsoft.copilot.eclipse.feature.feature.group' name='Github Copilot' version='0.0.0'>