Make the BlockSpan non-structural. We don't want to show an indent-guide for them.

src/Features/CSharp/Portable/Structure/Providers/ArrowExpressionClauseStructureProvider.cs

@@ -21,7 +21,7 @@ internal class ArrowExpressionClauseStructureProvider : AbstractSyntaxNodeStruct
                 isCollapsible: true,
                 textSpan: TextSpan.FromBounds(previousToken.Span.End, node.Span.End),
                 hintSpan: node.Parent.Span,
-                type: BlockTypes.Member));
+                type: BlockTypes.Nonstructural));
         }
     }
 }
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