delete redundant method of function `!=`, defined between bit floats
The method was originally added way back in commit
f1385790c103bb79e9878ecfaecf519c74a0051d.
Deleting the method preserves optimized `code_llvm` output, for example
with `code_llvm(!=, NTuple{2, Float64}; debuginfo=:none)`.
After PR #59509 deleted another such unnecessary method, this method is
the only nongeneric method of `!=` in the sysimage.