Elide broken but unnecessary `if` optimisations

Elide broken but unnecessary `if` optimisations

* lisp/emacs-lisp/byte-opt.el (byte-optimize-if):
Remove explicit clauses purposing to simplify

    (if X nil t) -> (not X)
    (if X t nil) -> (not (not X))

but never did so because of a coding mistake (eq instead of equal),
found by a recently added warning.  They weren't actually needed
thanks to the optimiser's fixpoint iteration: we eventually get the
same results through

    (if X nil t) -> (if (not X) t nil) -> (if (not X) t) -> (not X)
    (if X t nil) -> (if X t) -> (not (not X))