Add missing delete from rename

Signed-off-by: Matthias Hanel <mh@synadia.com>

server/gobackcomp/go113_prev.go

@@ -1,53 +0,0 @@
-// Copyright 2020 The NATS Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build !go1.13
-
-package gobackcomp
-
-// implements: go 1.13 errors.Unwrap(err error) error
-func errorsUnwrap(err error) error {
-	u, ok := err.(interface {
-		Unwrap() error
-	})
-	if !ok {
-		return nil
-	}
-	return u.Unwrap()
-}
-
-// implements: go 1.13 errors.Is(err, target error) bool
-func ErrorsIs(err, target error) bool {
-	// this is an outright copy of go 1.13 errors.Is(err, target error) bool
-	// removed isComparable
-	if target == nil {
-		return err == target
-	}
-
-	for {
-		if err == target {
-			return true
-		}
-		if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(target) {
-			return true
-		}
-		// TODO: consider supporing target.Is(err). This would allow
-		// user-definable predicates, but also may allow for coping with sloppy
-		// APIs, thereby making it easier to get away with them.
-		if err = errorsUnwrap(err); err == nil {
-			return false
-		}
-	}
-
-	return false
-}