Remove ConstFNeg

It's been removed in LLVM 16:
llvm/llvm-project@96cb7c2

Author: QuLogic

ir.go

@@ -918,7 +918,6 @@ func SizeOf(t Type) (v Value)              { v.C = C.LLVMSizeOf(t.C); return }
 func ConstNeg(v Value) (rv Value)          { rv.C = C.LLVMConstNeg(v.C); return }
 func ConstNSWNeg(v Value) (rv Value)       { rv.C = C.LLVMConstNSWNeg(v.C); return }
 func ConstNUWNeg(v Value) (rv Value)       { rv.C = C.LLVMConstNUWNeg(v.C); return }
-func ConstFNeg(v Value) (rv Value)         { rv.C = C.LLVMConstFNeg(v.C); return }
 func ConstNot(v Value) (rv Value)          { rv.C = C.LLVMConstNot(v.C); return }
 func ConstAdd(lhs, rhs Value) (v Value)    { v.C = C.LLVMConstAdd(lhs.C, rhs.C); return }
 func ConstNSWAdd(lhs, rhs Value) (v Value) { v.C = C.LLVMConstNSWAdd(lhs.C, rhs.C); return }