[WebNN] Fix the op support limit for batchNormalization (#25856)
### Description
<!-- Describe your changes. -->
According to the [WebNN
spec](https://www.w3.org/TR/webnn/#api-mlgraphbuilder-batchnorm), the
batchNorm should have input names "mean" and "variance" instead of
"input_mean" and "input_var".
### Motivation and Context
This issue causes any BatchNorm with mean/variance inputs to fall back
to wasm.