[CodeHealth] Use Position::anchorNode instead of deprecatedNode.

Source/core/editing/FormatBlockCommand.cpp

Index: Source/core/editing/FormatBlockCommand.cpp
diff --git a/Source/core/editing/FormatBlockCommand.cpp b/Source/core/editing/FormatBlockCommand.cpp
index 8e91f2643dffaf60c0d07fa68d5922bb1a54f40c..fde2ec2d862c5e29137e8ff4b40e8b92ec13afea 100644
--- a/Source/core/editing/FormatBlockCommand.cpp
+++ b/Source/core/editing/FormatBlockCommand.cpp
@@ -68,8 +68,8 @@ void FormatBlockCommand::formatRange(const Position& start, const Position& end,
     if (!root || !refElement)
         return;
 
-    Node* nodeToSplitTo = enclosingBlockToSplitTreeTo(start.deprecatedNode());
-    RefPtrWillBeRawPtr<Node> outerBlock = (start.deprecatedNode() == nodeToSplitTo) ? start.deprecatedNode() : splitTreeToNode(start.deprecatedNode(), nodeToSplitTo).get();
+    Node* nodeToSplitTo = enclosingBlockToSplitTreeTo(start.anchorNode());
+    RefPtrWillBeRawPtr<Node> outerBlock = (start.anchorNode() == nodeToSplitTo) ? start.anchorNode() : splitTreeToNode(start.anchorNode(), nodeToSplitTo).get();
     RefPtrWillBeRawPtr<Node> nodeAfterInsertionPosition = outerBlock;
     RefPtrWillBeRawPtr<Range> range = Range::create(document(), start, endOfSelection);