Minecraft Java Server: correct java 21 usage

apps/Minecraft Java Server/install

@@ -117,14 +117,15 @@ else
   # we know the version of minecraft in use
   # choose the appropriate version of java based on that
   # version <= 1.16.5 java 8
-  # version >= 1.17 java 17
+  # 1.17 <= version < 1.21 java 17
+  # version >= 1.21 java 21
   function version { echo "$@" | awk -F. '{ printf("%d%03d%03d\n", $1,$2,$3); }'; }
   if [ $(version $server_version) -le $(version "1.16.5") ]; then
     echo "Using Java 8 by default"
     java_selection="Java 8"
   elif [ $(version $server_version) -ge $(version "1.21") ]; then
-    echo "Using Java 17 by default"
-    java_selection="Java 17"
+    echo "Using Java 21 by default"
+    java_selection="Java 21"
   elif [ $(version $server_version) -ge $(version "1.17") ]; then
     echo "Using Java 17 by default"
     java_selection="Java 17"