Resolve typo in 2.x jdk version 21 (#17516)

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>
(cherry picked from commit f7742c2)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

buildSrc/src/main/java/org/opensearch/gradle/test/DistroTestPlugin.java

@@ -77,7 +77,7 @@
 import java.util.stream.Stream;
 
 public class DistroTestPlugin implements Plugin<Project> {
-    private static final String SYSTEM_JDK_VERSION = "21.0.6+71";
+    private static final String SYSTEM_JDK_VERSION = "21.0.6+7";
     private static final String SYSTEM_JDK_VENDOR = "adoptium";
     private static final String GRADLE_JDK_VERSION = "21.0.6+7";
     private static final String GRADLE_JDK_VENDOR = "adoptium";