fix: Don't prepend "begin stack" to blocks inserted from the flyout (#9911)

* fix: Don't prepend "begin stack" to blocks inserted from the flyout

* Switch block.workspace.isDragging for block.isDragging

packages/blockly/core/block_aria_composer.ts

@@ -258,7 +258,7 @@ function getParentInputLabel(block: BlockSvg) {
 function getBeginStackLabel(block: BlockSvg) {
   // Don't include the "begin stack" label for blocks that are moving
   // or blocks in the flyout
-  if (block.isInFlyout || block.workspace.isDragging()) return undefined;
+  if (block.isInFlyout || block.isDragging()) return undefined;
   return block.getRootBlock() === block
     ? Msg['BLOCK_LABEL_BEGIN_STACK']
     : undefined;