llm,readline: use errors.Is instead of simple == check (#3161)

This fixes some brittle, simple equality checks to use errors.Is. Since
go1.13, errors.Is is the idiomatic way to check for errors.

Co-authored-by: Jeffrey Morgan <jmorganca@gmail.com>

readline/history.go

@@ -62,7 +62,7 @@ func (h *History) Init() error {
 	for {
 		line, err := r.ReadString('\n')
 		if err != nil {
-			if err == io.EOF {
+			if errors.Is(err, io.EOF) {
 				break
 			}
 			return err