FUS: delete deprecated counter collector attribute

platform/platform-impl/src/com/intellij/internal/statistic/service/fus/collectors/CounterUsageCollectorEP.java

@@ -13,15 +13,11 @@ public class CounterUsageCollectorEP extends AbstractExtensionPointBean {
   @Attribute("groupId")
   public String groupID;
 
-  @Deprecated
-  @Attribute("group_id")
-  public String legacyGroupID;
-
   @Attribute("version")
   public int version;
 
   @Nullable
   public String getGroupId() {
-    return groupID != null ? groupID : legacyGroupID;
+    return groupID;
   }
 }

platform/platform-impl/src/com/intellij/internal/statistic/service/fus/collectors/FUCounterUsageLogger.java

@@ -124,7 +124,7 @@ public class FUCounterUsageLogger {
   @Nullable
   private FeatureUsageGroup findRegisteredGroupById(@NotNull String groupId) {
     if (!myGroups.containsKey(groupId)) {
-      LOG.warn("Cannot record event because group is not registered.");
+      LOG.warn("Cannot record event because group '" + groupId + "' is not registered.");
       return null;
     }
     return myGroups.get(groupId);