Merge branch 'stable-3.1' into stable-3.2

* stable-3.1:
  Bazel: Consume bazel-toolchains release from bazel mirror
  Align the recommended buildifier version with CI's
  crafting-changes: Add some info on Optional/Nullable
  Bump bazel-toolchains to 5.0.0
  Set version to 2.16.28-SNAPSHOT
  Set version to 2.16.27
  ForRef#check should permit internal users to read all refs
  Update git submodules
  Update highlightjs to 10.6.0
  Use NoteDb sequence seed for groups sequence initialization
  GroupsOnInit: Remove unused dependency on ReviewDb
  Use NoteDb sequence seed for accounts sequence initialization
  Do not use ReviewDb anymore when is disabled
  Elasticsearch: Discontinue EOL versions 7.2 and 7.3 support
  e2e-tests: Add SubmitChangeInBranch scenario
  Update developers based on gerritcodereview's list
  ForRef#check should permit internal users to read all refs

Change-Id: I72f7184e0de6ed8225c135ec21c8a83c9d211009
diff --git a/java/com/google/gerrit/elasticsearch/ElasticVersion.java b/java/com/google/gerrit/elasticsearch/ElasticVersion.java
index bba1577..5e72780 100644
--- a/java/com/google/gerrit/elasticsearch/ElasticVersion.java
+++ b/java/com/google/gerrit/elasticsearch/ElasticVersion.java
@@ -18,8 +18,6 @@
 import java.util.regex.Pattern;
 
 public enum ElasticVersion {
-  V7_2("7.2.*"),
-  V7_3("7.3.*"),
   V7_4("7.4.*"),
   V7_5("7.5.*"),
   V7_6("7.6.*"),
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
index e8cf3e9..8cd09e6 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
@@ -39,10 +39,6 @@
 
   private static String getImageName(ElasticVersion version) {
     switch (version) {
-      case V7_2:
-        return "blacktop/elasticsearch:7.2.1";
-      case V7_3:
-        return "blacktop/elasticsearch:7.3.2";
       case V7_4:
         return "blacktop/elasticsearch:7.4.2";
       case V7_5:
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java b/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java
index 1ec8a5d..508dc84 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java
@@ -22,12 +22,6 @@
 public class ElasticVersionTest {
   @Test
   public void supportedVersion() throws Exception {
-    assertThat(ElasticVersion.forVersion("7.2.0")).isEqualTo(ElasticVersion.V7_2);
-    assertThat(ElasticVersion.forVersion("7.2.1")).isEqualTo(ElasticVersion.V7_2);
-
-    assertThat(ElasticVersion.forVersion("7.3.0")).isEqualTo(ElasticVersion.V7_3);
-    assertThat(ElasticVersion.forVersion("7.3.1")).isEqualTo(ElasticVersion.V7_3);
-
     assertThat(ElasticVersion.forVersion("7.4.0")).isEqualTo(ElasticVersion.V7_4);
     assertThat(ElasticVersion.forVersion("7.4.1")).isEqualTo(ElasticVersion.V7_4);