Do not catch/rethrow ThreadDeath

In Java 21 Thread.stop simply throws UnsupportedOperationException and
ThreadDeath was thrown only from that method in older JVM versions.

ua/org.eclipse.help.base/src/org/eclipse/help/internal/base/BaseHelpSystem.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2021 IBM Corporation and others.
+ * Copyright (c) 2000, 2024 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -332,8 +332,6 @@ public static void runLiveHelp(String pluginID, String className, String arg) {
 				runnableLiveHelp.setDaemon(true);
 				runnableLiveHelp.start();
 			}
-		} catch (ThreadDeath td) {
-			throw td;
 		} catch (Exception e) {
 		}
 	}