[WebGPU] Fix subgroup matrix configs not populated in WASM builds (#33531)
### Description
<!-- Describe your changes. -->
Restore `adapter_info_.nextInChain = &subgroup_matrix_configs_` for WASM
builds in `WebGpuContext::Initialize`.
#33055 moved the ` #endif of the !defined(__wasm__)` block past this
assignment. As a result, on WASM `subgroup_matrix_configs_` is never
chained into `GetAdapterInfo()`. All subgroup matrix kernels will fall
back to
non subgroup matrix kernels.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
see above
Signed-off-by: Zhenwei Jin <zhenwei.jin@intel.com>