Remove obsolete "simple" field from CTabFolder

With the recent removal of curved tabs from
CTabFolder/CTabFolderRenderer, the CTabFolder property "simple" is
effectively always true. In order to avoid accidental usages and changes
of the according field, this change removes the field and makes the
accessors just always yield true.

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/CTabFolder.java

@@ -116,7 +116,6 @@ public class CTabFolder extends Composite {
 	/* sizing, positioning */
 	boolean onBottom = false;
 	boolean single = false;
-	boolean simple = true;
 	int fixedTabHeight = SWT.DEFAULT;
 	int tabHeight;
 	int minChars = 20;
@@ -1254,7 +1253,7 @@ public int getSelectionIndex() {
 @Deprecated(forRemoval = true, since = "2026-06")
 public boolean getSimple() {
 	checkWidget();
-	return simple;
+	return true;
 }
 /**
  * Returns <code>true</code> if the CTabFolder only displays the selected tab
@@ -2151,7 +2150,6 @@ void onResize(Event event) {
 			int x1 = Math.min(size.x, oldSize.x);
 			Rectangle trim = renderer.computeTrim(CTabFolderRenderer.PART_BODY, SWT.NONE, 0, 0, 0, 0);
 			if (size.x != oldSize.x) x1 -= trim.width + trim.x - marginWidth + 2;
-			if (!simple) x1 -= 5; // rounded top right corner
 			int y1 = Math.min(size.y, oldSize.y);
 			if (size.y != oldSize.y) y1 -= trim.height + trim.y - marginHeight;
 			int x2 = Math.max(size.x, oldSize.x);