(consolidated civil actions challenging interim decision partial deregulation of genetically engineered sugar beets; during pendency of action sugar beets were fully deregulated and interim decision expired; case dismissed as moot; court held because decision challenged had expired, there was no longer a case or controversy, so plaintiffs must demonstrate an exception to mootness doctrine; both sets of plaintiffs’ claims were not evading review due to timing and full deregulation decision could be challenged; claim was also not one likely to recur, so no exception to mootness doctrine applied).