Remove QuicEnableDefaultEnabledVersions Now that cl/290818515 has landed, we no longer need QuicEnableDefaultEnabledVersions() to ensure some versions are enabled, so we're removing it. NO_BUG=test-only cleanup gfe-relnote: n/a, test-only change PiperOrigin-RevId: 290845205 Change-Id: Ib18342e5dab32040a795a30dd3a311efc3dbfb2d