Remove unused typedef reco::electronephltseed_iterator

Typdef `electronephltseed_iterator' is defined twice in `reco' namespace
in DataFormats/EgammaReco and DataFormats/ParticleFlowReco. This cannot
be loaded into a single translation unit, othwerwise it triggers typedef
redefinition with different type error.

Git grep shows that these typedefs are not used in CMSSW code.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>