Fix license value in bower.json
Fix license value in bower.json

According to bower.json spec (https://github.com/bower/spec/blob/master/json.md#license), "license" value must be one of SPDX license identifiers (https://spdx.org/licenses), "BSD" is not a valid SPDX identifier.
webcomponents/polyfills,webcomponents/polyfills,webcomponents/polyfills