Link to Java 21 documentation (#4510)

Signed-off-by: Jacob Laursen <jacob-github@vindvejr.dk>

bundles/org.openhab.core/src/main/java/org/openhab/core/common/QueueingThreadPoolExecutor.java

@@ -31,7 +31,7 @@
  * This is a thread pool executor service, which works as a developer would expect it to work.
  * The default {@link ThreadPoolExecutor} does the following (see
  * <a href=
- * "https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/concurrent/ThreadPoolExecutor.html">the
+ * "https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/concurrent/ThreadPoolExecutor.html">the
  * official JavaDoc)</a>:
  * <ul>
  * <li>If fewer than corePoolSize threads are running, the Executor always prefers adding a new thread rather than

bundles/org.openhab.core/src/main/java/org/openhab/core/events/TopicEventFilter.java

@@ -31,7 +31,7 @@ public class TopicEventFilter implements EventFilter {
      * Constructs a new topic event filter.
      *
      * @param topicRegex the regular expression of a topic
-     * @see <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/Pattern.html">Java
+     * @see <a href="https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/regex/Pattern.html">Java
      *      Regex</a>
      */
     public TopicEventFilter(String topicRegex) {

bundles/org.openhab.core/src/main/java/org/openhab/core/events/TopicGlobEventFilter.java

@@ -23,7 +23,7 @@
  * of events based on an event topic.
  * 
  * The syntax for the filter is the glob syntax documented at
- * https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/nio/file/FileSystem.html#getPathMatcher(java.lang.String)
+ * https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/nio/file/FileSystem.html#getPathMatcher(java.lang.String)
  *
  * @author Cody Cutrer - Initial contribution
  */
@@ -37,7 +37,7 @@ public class TopicGlobEventFilter implements EventFilter {
      *
      * @param topicGlob the glob
      * @see <a href=
-     *      "https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/nio/file/FileSystem.html#getPathMatcher(java.lang.String)">Java
+     *      "https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/nio/file/FileSystem.html#getPathMatcher(java.lang.String)">Java
      *      Glob</a>
      */
     public TopicGlobEventFilter(String topicGlob) {