Revert "Add version 7.9.0"

This reverts commit 716972aed0cbde78f4a7336eada25a31325d68ec.

.ci/bwcVersions

@@ -20,5 +20,4 @@ BWC_VERSION:
   - "7.6.3"
   - "7.7.0"
   - "7.8.0"
-  - "7.9.0"
   - "8.0.0"

server/src/main/java/org/elasticsearch/Version.java

@@ -78,7 +78,6 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_7_6_3 = new Version(7060399, org.apache.lucene.util.Version.LUCENE_8_4_0);
     public static final Version V_7_7_0 = new Version(7070099, org.apache.lucene.util.Version.LUCENE_8_5_1);
     public static final Version V_7_8_0 = new Version(7080099, org.apache.lucene.util.Version.LUCENE_8_5_1);
-    public static final Version V_7_9_0 = new Version(7090099, org.apache.lucene.util.Version.LUCENE_8_5_1);
     public static final Version V_8_0_0 = new Version(8000099, org.apache.lucene.util.Version.LUCENE_8_5_1);
     public static final Version CURRENT = V_8_0_0;