Deleted the induction rule nat_induct2, which was too weak and not used even once.
Deleted the induction rule nat_induct2, which was too weak and not used even once.

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle