finally remove LookupElement#getGrouping() together with its ruby clients rework

platform/lang-api/src/com/intellij/codeInsight/lookup/LookupElement.java

@@ -77,13 +77,6 @@ public abstract class LookupElement extends UserDataHolderBase {
     presentation.setItemText(getLookupString());
   }
 
-  /**
-   * @deprecated use {@link com.intellij.codeInsight.completion.PrioritizedLookupElement}
-   */
-  public int getGrouping() {
-    return 0;
-  }
-
   @Nullable
   public <T> T as(Class<T> aClass) {
     //noinspection unchecked

platform/lang-api/src/com/intellij/codeInsight/lookup/LookupElementDecorator.java

@@ -102,11 +102,6 @@ public abstract class LookupElementDecorator<T extends LookupElement> extends Lo
     return myDelegate.hashCode();
   }
 
-  @Override
-  public int getGrouping() {
-    return myDelegate.getGrouping();
-  }
-
   @NotNull
   public static <T extends LookupElement> LookupElementDecorator<T> withInsertHandler(@NotNull T element, @NotNull final InsertHandler<? super LookupElementDecorator<T>> insertHandler) {
     return new InsertingDecorator<T>(element, insertHandler);

platform/lang-impl/src/com/intellij/codeInsight/completion/GroupingWeigher.java

@@ -14,6 +14,6 @@ public class GroupingWeigher extends CompletionWeigher {
       return -prioritized.getGrouping();
     }
 
-    return -element.getGrouping();
+    return 0;
   }
 }

platform/lang-impl/src/com/intellij/codeInsight/lookup/LookupItem.java

@@ -298,11 +298,6 @@ public class LookupItem<T> extends MutableLookupElement<T> implements Comparable
     return myPriority;
   }
 
-  @Override
-  public final int getGrouping() {
-    return myGrouping;
-  }
-
   @NotNull
   public LookupItem<T> setPresentableText(@NotNull final String displayText) {
     myPresentable = displayText;