Files.app: Remove unused private API "chrome.fileBrowserPrivate.getFileLocations".

"getFileLocations" is not used anywhere. We can remove it.

BUG=241695
TEST=Files.app

Review URL: https://chromiumcodereview.appspot.com/15255002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@200915 0039d316-1c4b-4281-b951-d872f2087c98