missed rename

Author: ToddGrun

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/TextDifferencing/TextDiffer.cs

@@ -229,5 +229,5 @@ private void FindChangeExtent(ref int lowA, ref int highA, ref int lowB, ref int
     }
 
     private bool SourceEqualUsingOffset(int oldSourceIndex, int newSourceIndex)
-        => SourceEqual(oldSourceIndex + _sourceOffsetA, newSourceIndex + _newSourceOffset);
+        => SourceEqual(oldSourceIndex + _oldSourceOffset, newSourceIndex + _newSourceOffset);
 }