webstorage: legacy platform objects should not override desc.[[Configurable]]

[panva]

During the process of updating WPTs the webstorage WPTs now exhibit a new failure.

[UNEXPECTED_FAILURE][FAIL] localStorage: defineProperty not configurable
assert_false: configurable expected false got true
    at Test.<anonymous> (/repo/node/test/fixtures/wpt/webstorage/symbol-props.window.js:42:9)
    at Test.step (/repo/node/test/fixtures/wpt/resources/testharness.js:2869:25)
    at test (/repo/node/test/fixtures/wpt/resources/testharness.js:633:30)
    at /repo/node/test/fixtures/wpt/webstorage/symbol-props.window.js:33:5
    at Array.forEach (<anonymous>)
Command: /repo/node/out/Release/node --test-reporter=./test/common/test-error-reporter.js,--test-reporter-destination=stdout /repo/node/test/wpt/test-webstorage.js 'symbol-props.window.js'

[UNEXPECTED_FAILURE][FAIL] sessionStorage: defineProperty not configurable
assert_false: configurable expected false got true
    at Test.<anonymous> (/repo/node/test/fixtures/wpt/webstorage/symbol-props.window.js:42:9)
    at Test.step (/repo/node/test/fixtures/wpt/resources/testharness.js:2869:25)
    at test (/repo/node/test/fixtures/wpt/resources/testharness.js:633:30)
    at /repo/node/test/fixtures/wpt/webstorage/symbol-props.window.js:33:5
    at Array.forEach (<anonymous>)
Command: /repo/node/out/Release/node --test-reporter=./test/common/test-error-reporter.js,--test-reporter-destination=stdout /repo/node/test/wpt/test-webstorage.js 'symbol-props.window.js'

refs: https://redirect.github.com/whatwg/webidl/commit/3fb6ab4
refs: https://redirect.github.com/web-platform-tests/wpt/commit/bb3f032503b3a15c9eb6dc7bf88cb9a52340edd4
refs: https://redirect.github.com/whatwg/webidl/issues/669

I will acknowledge these failures for now so that we can get WPT resources updated.

cc @cjihrig @anonrig