Delete SQL index support

Require the secondary index to be enabled in Gerrit 2.9.  Unless
configured differently, Lucene is used for the secondary index.

Change-Id: I3d2d804170835d69ffbfef586ddc3873ea3cd1c8

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RelatedChanges.java

@@ -198,7 +198,7 @@ class RelatedChanges extends TabPanel {
           }
         });
 
-    if (Gerrit.getConfig().hasIndex() && info.mergeable()) {
+    if (info.mergeable()) {
       StringBuilder conflictsQuery = new StringBuilder();
       conflictsQuery.append("status:open");
       conflictsQuery.append(" is:mergeable");