Remove reference to 7.9.4 relase which won't happen

.ci/bwcVersions

@@ -25,7 +25,6 @@ BWC_VERSION:
   - "7.9.1"
   - "7.9.2"
   - "7.9.3"
-  - "7.9.4"
   - "7.10.0"
   - "7.10.1"
   - "7.11.0"

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

@@ -84,7 +84,6 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_7_9_1 = new Version(7090199, org.apache.lucene.util.Version.LUCENE_8_6_2);
     public static final Version V_7_9_2 = new Version(7090299, org.apache.lucene.util.Version.LUCENE_8_6_2);
     public static final Version V_7_9_3 = new Version(7090399, org.apache.lucene.util.Version.LUCENE_8_6_2);
-    public static final Version V_7_9_4 = new Version(7090499, org.apache.lucene.util.Version.LUCENE_8_6_2);
     public static final Version V_7_10_0 = new Version(7100099, org.apache.lucene.util.Version.LUCENE_8_7_0);
     public static final Version V_7_10_1 = new Version(7100199, org.apache.lucene.util.Version.LUCENE_8_7_0);
     public static final Version V_7_11_0 = new Version(7110099, org.apache.lucene.util.Version.LUCENE_8_7_0);