Rename MLPool2dOptions::roundingType -> MLPool2dOptions::outputShapeRounding

[anssiko]

Update https://github.com/web-platform-tests/wpt/blob/master/webnn/conformance_tests/averagePool2d.https.any.js to match the rename:

MLPool2dOptions::roundingType -> MLPool2dOptions::outputShapeRounding

Spec:
https://www.w3.org/TR/webnn/#dictdef-mlpool2doptions
Spec commit:
webmachinelearning/webnn@a3e8163
Spec PR:
webmachinelearning/webnn#770

cc @BruceDai @mtavenrath

[mtavenrath]

The following tests have the same issue:
https://github.com/web-platform-tests/wpt/blob/master/webnn/conformance_tests/l2Pool2d.https.any.js
https://github.com/web-platform-tests/wpt/blob/master/webnn/conformance_tests/maxPool2d.https.any.js

[BruceDai]

Sorry for missing this issue. I'll upload CL to fix it ASAP.