Update StructuredBuffer-AST test after removal of HLSLResourceClassAttr (#108292)
In a previous PR, the `HLSLResourceClassAttr` attribute was removed from
the AST, in favor of using an attributed type that stores the same
information instead. This PR fixes test failures that assumed that
`HLSLResourceClassAttr` was still in the AST, and adjusts for the new
AST representation.