[hotfix][release] Add 1.18 to the flink version enum

Author: leonardBang

flink-annotations/src/main/java/org/apache/flink/FlinkVersion.java

@@ -54,7 +54,8 @@ public enum FlinkVersion {
     v1_14("1.14"),
     v1_15("1.15"),
     v1_16("1.16"),
-    v1_17("1.17");
+    v1_17("1.17"),
+    V1_18("1.18");
 
     private final String versionStr;