delete redundant method of function !=, defined between bit floats (#59518)

The method was originally added way back in commit
f138579.

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 two-argument method of `!=` in the sysimage.

Author: oscardssmith

base/float.jl

@@ -619,7 +619,6 @@ end
 
 ## floating point comparisons ##
 ==(x::T, y::T) where {T<:IEEEFloat} = eq_float(x, y)
-!=(x::T, y::T) where {T<:IEEEFloat} = ne_float(x, y)
 <( x::T, y::T) where {T<:IEEEFloat} = lt_float(x, y)
 <=(x::T, y::T) where {T<:IEEEFloat} = le_float(x, y)