delete redundant method of function !=, defined between types (#59509)

The method was originally added way back in PR #15575.

Pretty sure it is not necessary any more, as deleting it preserves the
effect inference.

Author: nsajko

base/operators.jl

@@ -293,7 +293,6 @@ isunordered(x::AbstractFloat) = isnan(x)
 isunordered(x::Missing) = true
 
 ==(T::Type, S::Type) = (@_total_meta; ccall(:jl_types_equal, Cint, (Any, Any), T, S) != 0)
-!=(T::Type, S::Type) = (@_total_meta; !(T == S))
 ==(T::TypeVar, S::Type) = false
 ==(T::Type, S::TypeVar) = false