[Telemetry] record_wpr shouldn't instantiate ProfileCreators

ProfileCreators inherit from the PageMeasurement class so record_wpr picks them up when it searches for all measurements in Telemetry. They are in fact not needed by record_wpr so this change removes them from the list.

BUG=319573

Review URL: https://codereview.chromium.org/77763003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236233 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236233